Saturday, 4 February 2017

EPA: Climate Change Indicators in the United States


I have been uploading pre-Trump page downloads from the US Environmental Protection Agency (EPA) website dealing with climate change, as a back-up for my own reference and potentially for others, before they are deleted or rewritten by climate change deniers. The EPA is under serious threat. Florida Congressman Matt Gaetz is drafting a bill calling for the agency to be completely abolished, so that US corporations can operate unhindered by environmental legislation. Funding for climate science has already been frozen, scientists have been gagged and now fear for their jobs and the future of climate science in the US.
This morning, we had the first evidence of changes to the EPA climate change website. See, for example: http://mashable.com/2017/02/03/trump-epa-climate-website-changes/#cYQFUGWs1SqL
So far the changes have focused on removing all mention of the USA's commitments to cooperating internationally on combatting climate change. The changes are likely to become more extensive when Trump's (climate change denier) appointment Scott Pruit is confirmed as EPA administrator.
This is a big deal at the global level, as during the Obama administration the USA was a world leader when it came to tackling climate change. Data and information, for example, on CO2 levels, temperature rise, sea ice melt etc., from US government organisations was a valuable resource for countries worldwide working to protect their citizens and infrastructure from the impacts of global climate change.
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Environment protection Agency (EPA): Climate Change Indicators in the United States

EPA has released the 2016 edition of Climate Change Indicators, which includes seven new indicators and a feature on climate and health.

The Earth's climate is changing. Temperatures are rising, snow and rainfall patterns are shifting, and more extreme climate events – like heavy rainstorms and record high temperatures – are already happening. Many of these observed changes are linked to the rising levels of carbon dioxide and other greenhouse gases in our atmosphere, caused by human activities. 

EPA partners with more than 40 data contributors from various government agencies, academic institutions, and other organizations to compile a key set of indicators related to the causes and effects of climate change. The indicators are published in EPA's report, Climate Change Indicators in the United States, available on this website and in print. Explore the indicators below.

Climate Change Indicators: Greenhouse Gases

Greenhouse gases from human activities are the most significant driver of observed climate change since the mid-20th century.1 The indicators in this chapter characterize emissions of the major greenhouse gases resulting from human activities, the concentrations of these gases in the atmosphere, and how emissions and concentrations have changed over time. When comparing emissions of different gases, these indicators use a concept called “global warming potential” to convert amounts of other gases into carbon dioxide equivalents.

As greenhouse gas emissions from human activities increase, they build up in the atmosphere and warm the climate, leading to many other changes around the world—in the atmosphere, on land, and in the oceans. The indicators in other chapters of this report illustrate many of these changes. These changes have both positive and negative effects on people, society, and the environment—including plants and animals. Because many of the major greenhouse gases stay in the atmosphere for tens to hundreds of years after being released, their warming effects on the climate persist over a long time and can therefore affect both present and future generations.

Summary of Key Points

  • U.S. Greenhouse Gas Emissions. In the United States, greenhouse gas emissions caused by human activities increased by 7 percent from 1990 to 2014. Since 2005, however, total U.S. greenhouse gas emissions have decreased by 7 percent. Carbon dioxide accounts for most of the nation’s emissions and most of the increase since 1990. Electricity generation is the largest source of greenhouse gas emissions in the United States, followed by transportation. Emissions per person have decreased slightly in the last few years.
    • Sources of Data on U.S. Greenhouse Gas Emissions. EPA has two key programs that provide data on greenhouse gas emissions in the United States: the Inventory of U.S. Greenhouse Gas Emissions and Sinks and the Greenhouse Gas Reporting Program. The programs are complementary, providing both a higher-level perspective on the nation’s total emissions and detailed information about the sources and types of emissions from individual facilities.
  • Global Greenhouse Gas Emissions. Worldwide, net emissions of greenhouse gases from human activities increased by 35 percent from 1990 to 2010. Emissions of carbon dioxide, which account for about three-fourths of total emissions, increased by 42 percent over this period. As with the United States, the majority of the world’s emissions result from electricity generation, transportation, and other forms of energy production and use.
  • Atmospheric Concentrations of Greenhouse Gases. Concentrations of carbon dioxide and other greenhouse gases in the atmosphere have increased since the beginning of the industrial era. Almost all of this increase is attributable to human activities.2 Historical measurements show that the current global atmospheric concentrations of carbon dioxide are unprecedented compared with the past 800,000 years, even after accounting for natural fluctuations.
  • Climate Forcing. Climate forcing refers to a change in the Earth’s energy balance, leading to either a warming or cooling effect over time. An increase in the atmospheric concentrations of greenhouse gases produces a positive climate forcing, or warming effect. From 1990 to 2015, the total warming effect from greenhouse gases added by humans to the Earth’s atmosphere increased by 37 percent. The warming effect associated with carbon dioxide alone increased by 30 percent.

Major Long-Lived Greenhouse Gases and Their Characteristics

Greenhouse gas
How it's produced
Average lifetime in the atmosphere
100-year global warming potential
Carbon dioxide
Emitted primarily through the burning of fossil fuels (oil, natural gas, and coal), solid waste, and trees and wood products. Changes in land use also play a role. Deforestation and soil degradation add carbon dioxide to the atmosphere, while forest regrowth takes it out of the atmosphere. 
see below*
1
Methane
Emitted during the production and transport of oil and natural gas as well as coal. Methane emissions also result from livestock and agricultural practices and from the anaerobic decay of organic waste in municipal solid waste landfills. 
12.4 years
28–36
Nitrous oxide
Emitted during agricultural and industrial activities, as well as during combustion of fossil fuels and solid waste. 
121 years
265–298
Fluorinated gases
A group of gases that contain fluorine, including hydrofluorocarbons, perfluorocarbons, and sulfur hexafluoride, among other chemicals. These gases are emitted from a variety of industrial processes and commercial and household uses and do not occur naturally. Sometimes used as substitutes for ozone-depleting substances such as chlorofluorocarbons (CFCs). 
A few weeks to thousands of years
Varies (the highest is sulfur hexfluoride at 23,500

This table shows 100-year global warming potentials, which describe the effects that occur over a period of 100 years after a particular mass of a gas is emitted. Global warming potentials and lifetimes come from the Intergovernmental Panel on Climate Change’s Fifth Assessment Report.3

* Carbon dioxide’s lifetime cannot be represented with a single value because the gas is not destroyed over time, but instead moves among different parts of the ocean–atmosphere–land system. Some of the excess carbon dioxide is absorbed quickly (for example, by the ocean surface), but some will remain in the atmosphere for thousands of years, due in part to the very slow process by which carbon is transferred to ocean sediments.

Sources of Data on U.S. Greenhouse Gas Emissions

EPA has two key programs that provide data on greenhouse gas emissions in the United States: the Inventory of U.S. Greenhouse Gas Emissions and Sinks and the Greenhouse Gas Reporting Program. The programs are complementary, providing both a higher-level perspective on the nation’s total emissions and detailed information about the sources and types of emissions from individual facilities. The data in EPA’s U.S. Greenhouse Gas Emissions indicator come from the national inventory.

EPA's Inventory of Greenhouse Gas Emissions and Sinks

EPA develops an annual report called the Inventory of U.S. Greenhouse Gas Emissions and Sinks (or the GHG Inventory). This report tracks trends in total annual U.S. emissions by source (or sink), economic sector, and greenhouse gas going back to 1990. EPA uses national energy data, data on national agricultural activities, and other national statistics to provide a comprehensive accounting of total greenhouse gas emissions for all man-made sources in the United States. This inventory fulfills the nation’s obligation to provide an annual emissions report under the United Nations Framework Convention on Climate Change.

EPA's Greenhouse Gas Reporting Program

EPA’s Greenhouse Gas Reporting Program collects annual emissions data from industrial sources that directly emit large amounts of greenhouse gases. Generally, facilities that emit more than 25,000 metric tons of carbon dioxide equivalents per year are required to report. The program also collects data from entities known as "suppliers" that supply certain fossil fuels and industrial gases that will emit greenhouse gases into the atmosphere if burned or released—for example, refineries that supply petroleum products such as gasoline. The Greenhouse Gas Reporting Program only requires reporting; it is not an emissions control program. This program helps EPA and the public understand where greenhouse gas emissions are coming from, and will improve our ability to make informed policy, business, and regulatory decisions.

EPA’s Greenhouse Gas Reporting Program provides facility-level information and allows people to track changes in greenhouse gas emissions in various industries, geographic areas, and industrial facilities. EPA has now verified three years of data and made them publicly available.

Learn more about the Greenhouse Gas Reporting Program and explore data by facility, industry, location, or gas using a data visualization and mapping tool called FLIGHT.

Why does it matter?

As greenhouse gas emissions from human activities increase, they build up in the atmosphere and warm the climate, leading to many other changes around the world—in the atmosphere, on land, and in the oceans. The indicators in other chapters of this report illustrate many of these changes. These changes have both positive and negative effects on people, society, and the environment—including plants and animals. Because many of the major greenhouse gases stay in the atmosphere for tens to hundreds of years after being released, their warming effects on the climate persist over a long time and can therefore affect both present and future generations.




References

1 IPCC (Intergovernmental Panel on Climate Change). 2013. Climate change 2013: The physical science basis. Working Group I contribution to the IPCC Fifth Assessment Report. Cambridge, United Kingdom: Cambridge University Press. www.ipcc.ch/report/ar5/wg1.

2 IPCC (Intergovernmental Panel on Climate Change). 2013. Climate change 2013: The physical science basis. Working Group I contribution to the IPCC Fifth Assessment Report. Cambridge, United Kingdom: Cambridge University Press. www.ipcc.ch/report/ar5/wg1.

3 IPCC (Intergovernmental Panel on Climate Change). 2013. Climate change 2013: The physical science basis. Working Group I contribution to the IPCC Fifth Assessment Report. Cambridge, United Kingdom: Cambridge University Press. www.ipcc.ch/report/ar5/wg1.

Climate Change Indicators: Weather and Climate

Rising global average temperature is associated with widespread changes in weather patterns. Scientific studies indicate that extreme weather events such as heat waves and large storms are likely to become more frequent or more intense with human-induced climate change. This chapter focuses on observed changes in temperature, precipitation, storms, floods, and droughts.

Long-term changes in climate can directly or indirectly affect many aspects of society in potentially disruptive ways. For example, warmer average temperatures could increase air conditioning costs and affect the spread of diseases like Lyme disease, but could also improve conditions for growing some crops. More extreme variations in weather are also a threat to society. More frequent and intense extreme heat events can increase illnesses and deaths, especially among vulnerable populations, and damage some crops. While increased precipitation can replenish water supplies and support agriculture, intense storms can damage property, cause loss of life and population displacement, and temporarily disrupt essential services such as transportation, telecommunications, energy, and water supplies.

Summary of Key Points

  • U.S. and Global Temperature. Average temperatures have risen across the contiguous 48 states since 1901, with an increased rate of warming over the past 30 years. Eight of the top 10 warmest years on record have occurred since 1998. Average global temperatures show a similar trend, and all of the top 10 warmest years on record worldwide have occurred since 1998. Within the United States, temperatures in parts of the North, the West, and Alaska have increased the most. 
  • High and Low Temperatures. Many extreme temperature conditions are becoming more common. Since the 1970s, unusually hot summer days (highs) have become more common over the last few decades in the United States. Unusually hot summer nights (lows) have become more common at an even faster rate. This trend indicates less “cooling off” at night. Although the United States has experienced many winters with unusually low temperatures, unusually cold winter temperatures have become less common—particularly very cold nights (lows). Record-setting daily high temperatures have become more common than record lows. The decade from 2000 to 2009 had twice as many record highs as record lows.
  • U.S. and Global Precipitation. Total annual precipitation has increased over land areas in the United States and worldwide. Since 1901, precipitation has increased at an average rate of 0.08 inches per decade over land areas worldwide. However, shifting weather patterns have caused certain areas, such as the Southwest, to experience less precipitation than usual.
  • Heavy Precipitation. In recent years, a higher percentage of precipitation in the United States has come in the form of intense single-day events. The prevalence of extreme single-day precipitation events remained fairly steady between 1910 and the 1980s but has risen substantially since then. Nationwide, nine of the top 10 years for extreme one-day precipitation events have occurred since 1990. The occurrence of abnormally high annual precipitation totals (as defined by the National Oceanic and Atmospheric Administration) has also increased.
  • Tropical Cyclone Activity. Tropical storm activity in the Atlantic Ocean, the Caribbean, and the Gulf of Mexico has increased during the past 20 years. Storm intensity is closely related to variations in sea surface temperature in the tropical Atlantic. However, changes in observation methods over time make it difficult to know for sure whether a longer-term increase in storm activity has occurred. Records collected since the late 1800s suggest that the actual number of hurricanes per year has not increased.
  • River Flooding. Increases and decreases in the frequency and magnitude of river flood events vary by region. Floods have generally become larger across parts of the Northeast and Midwest and smaller in the West, southern Appalachia, and northern Michigan. Large floods have become more frequent across the Northeast, Pacific Northwest, and parts of the northern Great Plains, and less frequent in the Southwest and the Rockies.
  • Drought. Average drought conditions across the nation have varied since records began in 1895. The 1930s and 1950s saw the most widespread droughts, while the last 50 years have generally been wetter than average. However, specific trends vary by region. A more detailed index developed recently shows that over the period from 2000 through 2015, roughly 20 to 70 percent of the U.S. land area experienced conditions that were at least abnormally dry at any given time. However, this index has not been in use for long enough to compare with historical drought patterns. 
    • A Closer Look: Temperature and Drought in the Southwest. The southwestern United States is particularly sensitive to changes in temperature and thus vulnerable to drought, as even a small decrease in water availability in this already arid region can stress natural systems and further threaten water supplies.

Why does it matter?

Long-term changes in climate can directly or indirectly affect many aspects of society in potentially disruptive ways. For example, warmer average temperatures could increase air conditioning costs and affect the spread of diseases like Lyme disease, but could also improve conditions for growing some crops. More extreme variations in weather are also a threat to society. More frequent and intense extreme heat events can increase illnesses and deaths, especially among vulnerable populations, and damage some crops. While increased precipitation can replenish water supplies and support agriculture, intense storms can damage property, cause loss of life and population displacement, and temporarily disrupt essential services such as transportation, telecommunications, energy, and water supplies.

Climate Change Indicators: Oceans

Covering about 70 percent of the Earth’s surface, the world’s oceans have a two-way relationship with weather and climate. The oceans influence the weather on local to global scales, while changes in climate can fundamentally alter many properties of the oceans. This chapter examines how some of these important characteristics of the oceans have changed over time.

As greenhouse gases trap more energy from the sun, the oceans are absorbing more heat, resulting in an increase in sea surface temperatures and rising sea level. Changes in ocean temperatures and currents brought about by climate change will lead to alterations in climate patterns around the world. For example, warmer waters may promote the development of stronger storms in the tropics, which can cause property damage and loss of life. The impacts associated with sea level rise and stronger storms are especially relevant to coastal communities.

Although the oceans help reduce climate change by storing large amounts of carbon dioxide, increasing levels of dissolved carbon are changing the chemistry of seawater and making it more acidic. Increased ocean acidity makes it more difficult for certain organisms, such as corals and shellfish, to build their skeletons and shells. These effects, in turn, could substantially alter the biodiversity and productivity of ocean ecosystems.

Changes in ocean systems generally occur over much longer time periods than in the atmosphere, where storms can form and dissipate in a single day. Interactions between the oceans and atmosphere occur slowly over many months to years, and so does the movement of water within the oceans, including the mixing of deep and shallow waters. Thus, trends can persist for decades, centuries, or longer. For this reason, even if greenhouse gas emissions were stabilized tomorrow, it would take many more years—decades to centuries—for the oceans to adjust to changes in the atmosphere and the climate that have already occurred.

Summary of Key Points

  • Ocean HeatThree independent analyses show that the amount of heat stored in the ocean has increased substantially since the 1950s. Ocean heat content not only determines sea surface temperature, but also affects sea level and currents. 
  • Sea Surface Temperature. Ocean surface temperatures increased around the world during the 20th century. Even with some year-to-year variation, the overall increase is clear, and sea surface temperatures have been consistently higher during the past three decades than at any other time since reliable observations began in the late 1800s.
  • Sea Level. When averaged over all of the world’s oceans, sea level has risen at a rate of roughly six-tenths of an inch per decade since 1880. The rate of increase has accelerated in recent years to more than an inch per decade. Changes in sea level relative to the land vary by region. Along the U.S. coastline, sea level has risen the most along the Mid-Atlantic coast and parts of the Gulf coast, where some stations registered increases of more than 8 inches between 1960 and 2015. Sea level has decreased relative to the land in parts of Alaska and the Pacific Northwest. 
    • A Closer Look: Land Loss Along the Atlantic Coast. As sea level rises, dry land and wetlands can turn into open water. Along many parts of the Atlantic coast, this problem is made worse by low elevations and land that is already sinking. Between 1996 and 2011, the coastline from Florida to New York lost more land than it gained.
  • Coastal Flooding. Flooding is becoming more frequent along the U.S. coastline as sea level rises. Nearly every site measured has experienced an increase in coastal flooding since the 1950s. The rate is accelerating in many locations along the East and Gulf coasts. The Mid-Atlantic region suffers the highest number of coastal flood days and has also experienced the largest increases in flooding.
  • Ocean Acidity. The ocean has become more acidic over the past few decades because of increased levels of atmospheric carbon dioxide, which dissolves in the water. Higher acidity affects the balance of minerals in the water, which can make it more difficult for certain marine animals to build their protective skeletons or shells.

Why does it matter?

As greenhouse gases trap more energy from the sun, the oceans are absorbing more heat, resulting in an increase in sea surface temperatures and rising sea level. Changes in ocean temperatures and currents brought about by climate change will lead to alterations in climate patterns around the world. For example, warmer waters may promote the development of stronger storms in the tropics, which can cause property damage and loss of life. The impacts associated with sea level rise and stronger storms are especially relevant to coastal communities.

Although the oceans help reduce climate change by storing large amounts of carbon dioxide, increasing levels of dissolved carbon are changing the chemistry of seawater and making it more acidic. Increased ocean acidity makes it more difficult for certain organisms, such as corals and shellfish, to build their skeletons and shells. These effects, in turn, could substantially alter the biodiversity and productivity of ocean ecosystems.

Changes in ocean systems generally occur over much longer time periods than in the atmosphere, where storms can form and dissipate in a single day. Interactions between the oceans and atmosphere occur slowly over many months to years, and so does the movement of water within the oceans, including the mixing of deep and shallow waters. Thus, trends can persist for decades, centuries, or longer. For this reason, even if greenhouse gas emissions were stabilized tomorrow, it would take many more years—decades to centuries—for the oceans to adjust to changes in the atmosphere and the climate that have already occurred.

Climate Change Indicators: Snow and Ice

The Earth’s surface contains many forms of snow and ice, including sea, lake, and river ice; snow cover; glaciers, ice caps, and ice sheets; and frozen ground. Climate change can dramatically alter the Earth’s snow- and ice-covered areas because snow and ice can easily change between solid and liquid states in response to relatively minor changes in temperature. This chapter focuses on trends in snow, glaciers, and the freezing and thawing of oceans and lakes.

Reduced snowfall and less snow cover on the ground could diminish the beneficial insulating effects of snow for vegetation and wildlife, while also affecting water supplies, transportation, cultural practices, travel, and recreation for millions of people. For communities in Arctic regions, reduced sea ice could increase coastal erosion and exposure to storms, threatening homes and property, while thawing ground could damage roads and buildings and accelerate erosion. Conversely, reduced snow and ice could present commercial opportunities for others, including ice-free shipping lanes and increased access to natural resources.

Such changing climate conditions can have worldwide implications because snow and ice influence air temperatures, sea level, ocean currents, and storm patterns. For example, melting ice sheets on Greenland and Antarctica add fresh water to the ocean, increasing sea level and possibly changing ocean circulation that is driven by differences in temperature and salinity. Because of their light color, snow and ice also reflect more sunlight than open water or bare ground, so a reduction in snow cover and ice causes the Earth’s surface to absorb more energy from the sun and become warmer.

Summary of Key Points

  • Arctic Sea Ice. Part of the Arctic Ocean is covered by ice year-round. The area covered by ice is typically smallest in September, after the summer melting season. The annual minimum extent of Arctic sea ice has decreased over time, and in September 2012 it was the smallest ever recorded. The length of the melt season for Arctic ice has grown, and the ice has also become thinner, which makes it more vulnerable to further melting.
  • Antarctic Sea Ice. Antarctic sea ice extent in September and February has increased somewhat over time. The September maximum extent reached the highest level on record in 2014—about 7 percent larger than the 1981­–2010 average. Slight increases in Antarctic sea ice are outweighed by the loss of sea ice in the Arctic during the same time period, however.
  • Glaciers. Glaciers in the United States and around the world have generally shrunk since the 1960s, and the rate at which glaciers are melting has accelerated over the last decade. The loss of ice from glaciers has contributed to the observed rise in sea level. 
  • Lake Ice. Lakes in the northern United States are freezing later and thawing earlier compared with the 1800s and early 1900s. Freeze dates have shifted later at a rate of roughly half a day to one-and-a-half days per decade. All of the lakes studied were also found to be thawing earlier in the year, with spring thaw dates growing earlier by up to 24 days in the past 110 years.
    • Community Connection: Ice Breakup in Two Alaskan Rivers. Regions in the far north are warming more quickly than other parts of the world. Two long-running contests on the Tanana and Yukon rivers in Alaska—where people guess the date when the river ice will break up in the spring—provide a century’s worth of evidence revealing that the ice on these rivers is generally breaking up earlier in the spring than it once did.
  • Snowfall. Total snowfall—the amount of snow that falls in a particular location—has decreased in most parts of the country since widespread records began in 1930. One reason for this decline is that nearly 80 percent of the locations studied have seen more winter precipitation fall in the form of rain instead of snow.
  • Snow Cover. Snow cover refers to the area of land that is covered by snow at any given time. Between 1972 and 2015, the average portion of North America covered by snow decreased at a rate of about 3,300 square miles per year, based on weekly measurements taken throughout the year. There has been much year-to-year variability, however. The length of time when snow covers the ground has become shorter by nearly two weeks since 1972, on average.
  • Snowpack. The depth of snow on the ground (snowpack) in early spring decreased at more than 90 percent of measurement sites in the western United States between 1955 and 2016. Across all sites, snowpack depth declined by an average of 23 percent during this time period.


Reduced snowfall and less snow cover on the ground could diminish the beneficial insulating effects of snow for vegetation and wildlife, while also affecting water supplies, transportation, cultural practices, travel, and recreation for millions of people. For communities in Arctic regions, reduced sea ice could increase coastal erosion and exposure to storms, threatening homes and property, while thawing ground could damage roads and buildings and accelerate erosion. Conversely, reduced snow and ice could present commercial opportunities for others, including ice-free shipping lanes and increased access to natural resources.

Such changing climate conditions can have worldwide implications because snow and ice influence air temperatures, sea level, ocean currents, and storm patterns. For example, melting ice sheets on Greenland and Antarctica add fresh water to the ocean, increasing sea level and possibly changing ocean circulation that is driven by differences in temperature and salinity. Because of their light color, snow and ice also reflect more sunlight than open water or bare ground, so a reduction in snow cover and ice causes the Earth’s surface to absorb more energy from the sun and become warmer.

Climate Change Indicators: Health and Society


Changes in the Earth’s climate can affect public health, agriculture, water supplies, energy production and use, land use and development, and recreation. The nature and extent of these effects, and whether they will be harmful or beneficial, will vary regionally and over time. This chapter looks at some of the ways that climate change is affecting human health and society, including changes in Lyme disease, West Nile virus, ragweed pollen season, heat-related deaths and hospitalizations, heating and cooling needs, and the agricultural growing season across the United States.

Because impacts on human health are complex, often indirect, and dependent on multiple societal and environmental factors (including how people choose to respond to these impacts), the development of appropriate health-related climate indicators is challenging and still emerging. It is important for health-related climate indicators to be clear, measurable, and timely to better understand the link between climate change and health effects.

Changes in climate affect the average weather conditions to which we are accustomed. These changes may result in multiple threats to human health and welfare. Warmer average temperatures will likely lead to hotter days and more frequent and longer heat waves, which could increase the number of heat-related illnesses and deaths. Increases in the frequency or severity of extreme weather events, such as storms, could increase the risk of dangerous flooding, high winds, and other direct threats to people and property. Warmer temperatures could also reduce air quality by increasing the chemical reactions that produce smog, and, along with changes in precipitation patterns and extreme events, could enhance the spread of some diseases.

In addition, climate change could require adaptation on larger and faster scales than in the past, presenting challenges to human well-being and the economy. The more extensively and more rapidly the climate changes, the larger the potential effects on society. The extent to which climate change will affect different regions and sectors of society will depend not only on the sensitivity of those systems to climate change, but also on their ability to adapt to or cope with climate change. Populations of particular concern include the poor, the elderly, those already in poor health, the disabled, and indigenous populations.

Summary of Key Points

  • Heat-Related Deaths. Since 1979, more than 9,000 Americans were reported to have died as a direct result of heat-related illnesses such as heat stroke. The annual death rate is higher when accounting for deaths in which heat was reported as a contributing factor, including the interaction of heat and cardiovascular disease. People aged 65+ are a particular concern: a growing demographic group that is several times more likely to die from heat-related cardiovascular disease than the general population. Considerable year-to-year variability and certain limitations of the underlying data for this indicator make it difficult to determine whether the United States has experienced long-term trends in the number of deaths classified as “heat-related.” 
  • Heat-Related Illness. From 2001 to 2010, a total of about 28,000 heat-related hospitalizations were recorded across 20 states. Annual heat-related hospitalization rates ranged from fewer than one case per 100,000 people in some states to nearly four cases per 100,000 people in others. People aged 65+ accounted for more heat-related hospitalizations than any other age group from 2001 to 2010, and males were hospitalized for heat-related illnesses more than twice as often as females. 
  • Heating and Cooling Degree Days. Heating and cooling degree days measure the difference between outdoor temperatures and the temperatures that people find comfortable indoors. As the U.S. climate has warmed in recent years, heating degree days have decreased and cooling degree days have increased overall, suggesting that Americans need to use less energy for heating and more energy for air conditioning. This pattern stands out the most in the North and West, while much of the Southeast has experienced the opposite results.
  • Lyme Disease. Lyme disease is a bacterial illness spread by ticks that bite humans. Tick habitat and populations are influenced by many factors, including climate. Nationwide, the rate of reported cases of Lyme disease has approximately doubled since 1991. The number and distribution of reported cases of Lyme disease have increased in the Northeast and upper Midwest over time, where some states now report 50 to 100 more cases of Lyme disease per 100,000 people than they did in 1991.
  • West Nile Virus. West Nile virus is spread by mosquitoes, whose habitat and populations are influenced by temperature and water availability. The incidence of West Nile virus neuroinvasive disease in the United States has varied widely from year to year and among geographic regions since tracking began in 2002. Variation in disease incidence is affected by climate and many other factors, and no obvious long-term trend can be detected yet through this limited data set.
  • Length of Growing Season. The length of the growing season for crops has increased in almost every state. States in the Southwest (e.g., Arizona and California) have seen the most dramatic increase. In contrast, the growing season has actually become shorter in a few southeastern states. The observed changes reflect earlier spring warming as well as later arrival of fall frosts. The length of the growing season has increased more rapidly in the West than in the East.
  • Ragweed Pollen Season. Warmer temperatures and later fall frosts allow ragweed plants to produce pollen later into the year, potentially prolonging the allergy season for millions of people. The length of ragweed pollen season has increased at 10 out of 11 locations studied in the central United States and Canada since 1995. The change becomes more pronounced from south to north. 

Why does it matter?

Changes in climate affect the average weather conditions to which we are accustomed. These changes may result in multiple threats to human health and welfare. Warmer average temperatures will likely lead to hotter days and more frequent and longer heat waves, which could increase the number of heat-related illnesses and deaths. Increases in the frequency or severity of extreme weather events, such as storms, could increase the risk of dangerous flooding, high winds, and other direct threats to people and property. Warmer temperatures could also reduce air quality by increasing the chemical reactions that produce smog, and, along with changes in precipitation patterns and extreme events, could enhance the spread of some diseases.

In addition, climate change could require adaptation on larger and faster scales than in the past, presenting challenges to human well-being and the economy. The more extensively and more rapidly the climate changes, the larger the potential effects on society. The extent to which climate change will affect different regions and sectors of society will depend not only on the sensitivity of those systems to climate change, but also on their ability to adapt to or cope with climate change. Populations of particular concern include the poor, the elderly, those already in poor health, the disabled, and indigenous populations.

Climate Change Indicators: Ecosystems

Ecosystems provide humans with food, clean water, and a variety of other services that canbe affected by climate change. This chapter looks at some of the ways that climate change affects ecosystems, including changes in wildfires, streams and lakes, bird migration patterns, fish and shellfish populations, and plant growth.

Changes in the Earth’s climate can affect ecosystems by altering the water cycle, habitats, animal behavior—such as nesting and migration patterns—and the timing of natural processes such as flower blooms. Changes that disrupt the functioning of ecosystems may increase the risk of harm or even extinction for some species. While wildfires occur naturally, more frequent and more intense fires can significantly disrupt ecosystems, damage property, put people and communities at risk, and create air pollution problems even far away from the source.

While plants and animals have adapted to environmental change for millions of years, the climate changes being experienced now could require adaptation on larger and faster scales than current species have successfully achieved in the past, thus increasing the risk of extinction or severe disruption for many species.

Summary of Key Points

  • Wildfires. Since 1983, the United States has had an average of 72,000 recorded wildfires per year. Of the 10 years with the largest acreage burned since 1983, nine have occurred since 2000 with many of the largest increases occurring in western states. The proportion of burned land suffering severe damage each year has ranged from 5 to 21 percent.
  • Streamflow. Changes in temperature, precipitation, snowpack, and glaciers can affect the rate of streamflow and the timing of peak flow. Over the last 75 years, minimum, maximum, and average flows have changed in many parts of the country—some higher, some lower. Most of the rivers and streams measured show peak winter-spring runoff happening at least five days earlier than it did in the mid-20th century.
  • Stream Temperature. Stream temperatures have risen throughout the Chesapeake Bay region (the area of focus for this indicator). From 1960 through 2014, water temperature increased at 79 percent of the stream sites measured in the region. Temperature has risen by an average of 1.2°F across all sites and 2.2°F at the sites where trends were statistically significant.
    • Tribal Connection: Trends in Stream Temperature in the Snake River. Between 1960 and 2015, water temperatures increased by 1.4°F in the Snake River at a site in eastern Washington. Several species of salmon use the Snake River to migrate and spawn, and these salmon play an important role in the diet, culture, religion, and economy of the region’s Native Americans.
  • Great Lakes Water Levels. Water levels in most of the Great Lakes appear to have declined in the last few decades. However, the most recent levels are all within the range of historical variation. Water levels in lakes are influenced by water temperature, which affects evaporation rates and ice formation. Since 1995, average surface water temperatures have increased slightly for each of the Great Lakes.
  • Bird Wintering Ranges. Some birds shift their range or alter their migration habits to adapt to changes in temperature or other environmental conditions. Long-term studies have found that bird species in North America have shifted their wintering grounds northward by an average of more than 40 miles since 1966, with several species shifting by hundreds of miles. On average, bird species have also moved their wintering grounds farther from the coast, consistent with inland winter temperatures becoming less severe.
  • Marine Species Distribution. The average center of biomass for 105 marine fish and invertebrate species along U.S. coasts shifted northward by about 10 miles between 1982 and 2015. These species also moved an average of 20 feet deeper. Shifts have occurred among several economically important fish and shellfish species. For example, American lobster, black sea bass, and red hake in the Northeast have moved northward by an average of 119 miles.
  • Leaf and Bloom Dates. Leaf growth and flower blooms are examples of natural events whose timing can be influenced by climate change. Observations of lilacs and honeysuckles in the contiguous 48 states suggest that first leaf dates and bloom dates show a great deal of year-to-year variability. Leaf and bloom events are generally happening earlier throughout the North and West but later in much of the South.
    • Community Connection: Cherry Blossom Bloom Dates in Washington, D.C. Peak bloom dates of the iconic cherry trees in Washington, D.C., recorded since the 1920s, indicate that cherry trees are blooming slightly earlier than in the past. Bloom dates are key to planning the Cherry Blossom Festival, one of the region’s most popular spring attractions.

Why does it matter?

Changes in the Earth’s climate can affect ecosystems by altering the water cycle, habitats, animal behavior—such as nesting and migration patterns—and the timing of natural processes such as flower blooms. Changes that disrupt the functioning of ecosystems may increase the risk of harm or even extinction for some species. While wildfires occur naturally, more frequent and more intense fires can significantly disrupt ecosystems, damage property, put people and communities at risk, and create air pollution problems even far away from the source.

While plants and animals have adapted to environmental change for millions of years, the climate changes being experienced now could require adaptation on larger and faster scales than current species have successfully achieved in the past, thus increasing the risk of extinction or severe disruption for many species.

Frequently asked questions about Climate Change Indicators

What is an indicator?

One important way to track and communicate the causes and effects of climate change is through the use of indicators. An indicator represents the state or trend of certain environmental or societal conditions over a given area and a specified period of time. The indicators in this report are designed to help readers understand observed long-term trends related to the causes and effects of climate change. In other words, they provide important evidence of "what climate change looks like." For example, long-term measurements of temperature in the United States and globally are used as an indicator to track and better understand the effects of changes in the Earth's climate.

Why does EPA compile and publish climate change indicators?

EPA compiles these indicators with the primary goal of informing readers' understanding of climate change. They are designed so that the public, scientists, analysts, decision-makers, educators, and others can use climate change indicators as a tool for:

  • Effectively communicating relevant climate science information in a sound, transparent, and easy-to-understand way.
  • Assessing trends in environmental quality, factors that influence the environment, and effects on ecosystems and society.
  • Informing science-based decision-making.

EPA publishes 37 indicators both online and in a summarized print edition to help readers understand changes observed from long-term records related to the causes and effects of climate change, the significance of these changes, and their possible consequences for people, the environment, and society. The indicators presented here do not cover all possible measures of the causes and effects of climate change, nor all possible climate change indicators found in the full body of scientific literature. Instead, these 37 indicators represent a select but wide-ranging set of high-quality, long-term data that show observed changes in the Earth's climate system and several climate-relevant impacts. Together, these indicators present compelling evidence that climate change is happening now in the United States and globally.

How do the indicators relate to climate change?

All of the indicators on this website relate to either the causes or effects of climate change. Some indicators show trends that can be more directly linked to human-induced climate change than others. Collectively, the trends depicted in these indicators provide important evidence of "what climate change looks like."

Although each indicator has a connection to climate change, EPA's indicators do not attempt to identify either the extent to which a certain indicator is driving climate change, nor the relative role of climate change in causing a trend in an observed indicator. Connections between human activities, climate change, and observed indicators are explored in more detail elsewhere in the scientific literature. For example, see the U.S. Global Change Research Program's National Climate Assessment.

Some indicators are directly linked to human activities that cause climate change, such as Global Greenhouse Gas Emissions. Changes depicted by other indicators, such as U.S. and Global Temperature, have been confidently linked with the increase in greenhouse gases caused by human activity. Some of the trends in other indicators, such as Wildfires, are consistent with what one would expect in a warming climate but may also be influenced by limitations in the historical data or other factors in addition to climate change. A few indicators, like West Nile Virus, though known to be influenced by climate change, do not yet show any significant trend. In some cases, this could be because the period for which data are available or the geographic scale in which they are presented is limited.

Where do the indicator data come from?

EPA partners with over 40 data contributors from various government agencies, academic institutions, and other organizations to compile and communicate key indicators related to the causes and effects of climate change. The indicators consist of peer-reviewed, publicly-available data from a number of government agencies, academic institutions, and other organizations. In addition to being published here, these data sets have been published in the scientific literature and in other government or academic reports. Details on each underlying data set as well as where to find it are provided in the technical documentation.

What geographic areas and time periods do the indicators cover?

Trends relevant to climate change are best viewed at broad geographic scales and over long time periods rather than at localized scales or over a few years or a season. EPA's indicators are based on historical records that go back in time as far as possible without sacrificing data quality, so each indicator's time scale varies.

Most of EPA's indicators focus on the United States. However, some include global trends to provide context or a basis for comparison, or because they are intrinsically global in nature, such as Atmospheric Concentrations of Greenhouse Gases. EPA attempts to present multiple scales (national, regional, or location-specific) in cases where the underlying data allow such scaling. The geographic extent and timeframe that each indicator represents largely depend on data availability and the nature of what is being measured.

Why do some indicator trends fluctuate over time?

Although the climate is continually changing, not every climate change indicator shows a constant pattern of steady change. The Earth is a complex system, and there are always natural variations from one year to the next—for example, a very warm year followed by a colder year. The Earth's climate also goes through other natural cycles that play out over a period of several years or even decades. Individual years or even individual decades can deviate from the long-term trend. Human factors may also influence a trend—for example, human activities and land management practices can affect wildfire activity from year to year.

How are EPA's indicators chosen and developed?

EPA chooses its indicators using a set of general assessment factors and a standard set of criteria that considers data quality, transparency of analytical methods, and relevance to climate change. Based on the availability of this data, some indicators present a single measure or variable; others have multiple measures, reflecting different data sources or different ways to group, characterize, or zoom in on the data. See the technical documentation overview for a full description of these general assessment factors and criteria and for a description of EPA's process for evaluating, reviewing, and publishing indicators.

EPA's climate change indicators and the accompanying technical documentation are designed to ensure that the science and underlying peer-reviewed data are presented and documented transparently. EPA also receives feedback from scientists, researchers, and communication experts to help inform the content and new features of EPA's indicators. The entire set of indicators, including the technical support documentation, is then peer-reviewed by independent technical experts.

Which greenhouse gases do these indicators track?

EPA's greenhouse gas-related indicators focus on most of the major, well-mixed greenhouse gases that contribute to the vast majority of warming of the climate when they are emitted into the atmosphere. These major gases are carbon dioxide, methane, nitrous oxide, and fluorinated gases. Some of these gases are produced almost entirely by human activities, while others come from a combination of natural sources and human activities.

Many of these major greenhouse gases remain in the atmosphere for tens to thousands of years after being released. They become globally mixed in the lower part of the atmosphere, called the troposphere (the first several miles above the Earth's surface), reflecting the combined emissions worldwide from the past and present. Due to this global mixing, concentrations of these gases are fairly similar no matter where in the world they are measured.

EPA's report also notes some other substances that have much shorter atmospheric lifetimes (i.e., less than a year) but are still relevant to climate change. Important short-lived substances that affect the climate include water vapor, ozone in the troposphere, pollutants that lead to ozone formation, and aerosols (atmospheric particles) such as black carbon and sulfates. Water vapor, tropospheric ozone, and black carbon contribute to warming, while other aerosols produce a cooling effect. In addition to several long-lived greenhouse gases, EPA's Atmospheric Concentrations of Greenhouse Gases indicator tracks concentrations of ozone in the layers of the Earth's atmosphere, while Figure 2 of the Climate Forcing indicator shows the influence of a variety of short-lived substances.

How do indicators relate to human health?

Indicators provide key information on changes that are occurring in our environment, like increasing temperatures or more severe extreme weather events, which can threaten people's health. Tracking changes in climate impacts and exposures improves understanding of changes in health risk, even if the actual health outcome is difficult to quantify. For example, while only some indicators exist for human health outcomes related to climate change, like West Nile Virus, Lyme Disease, and Heat-Related Deaths, other indicators—like Ragweed Pollen Season or Wildfires—give insight into the changing risks to human health. There are many factors other than climate that affect human health; these are discussed in more detail in EPA's full section on the connections between climate change and human health.


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