In the future, the EPA will be looking closely at bird migration patterns and counts of heat-related deaths, as well as changes in the oceans, glaciers and atmosphere, as it determines how to respond to a changing climate.
The agency released a list of 24 climate change indicators Tuesday that it intends to rely on when deciding how best to use its policy-making and program management resources to respond to climate change and evaluating the success of those efforts. The EPA is still focused on mitigating climate change through efforts to cut greenhouse gas emissions, but the list shows it is moving on to adaptation, as well.
Some of the indicators are based on fairly straightforward data gathered in much the same manner for over a century, such as temperature and precipitation. Others, the EPA notes, are new measurements that have been defined and collected over only the past few decades, such as heat-related deaths and climate forcing.
"These indicators show us that climate change is a very real problem with impacts that are already being seen," said Gina McCarthy, assistant administrator for EPA's Office of Air and Radiation.
The 24 climate change indicators and some of the agency's related findings so far are:
U.S. Greenhouse Gas Emissions: From 1990 to 2008, U.S. greenhouse gas emissions from human activities, such as transportation and electricity generation, increased 14 percent to 6,957 million metric tons of carbon dioxide equivalents. Emissions of carbon dioxide, the primary greenhouse gas, increased 16 percent.
Global Greenhouse Gas Emissions: Worldwide emissions of human-caused greenhouse gases rose 26 percent from 1990 to 2005, to 38,000 million metric tons of carbon dioxide equivalents. Emissions of fluorinated compounds, some with global warming potentials thousands of times greater than CO2, more than doubled. CO2, accounting for three-quarters of all global emissions, increased 31 percent.
Atmospheric Concentrations of Greenhouse Gases: Greenhouse gas concentrations are higher now than they have been in thousands of years, "even after accounting for natural fluctuations," the EPA says. Since the industrial revolution, they have risen from about 270 ppm to close to 390 ppm.
Climate Forcing: From 1990 to 2008, scientists calculated a 26 percent increase in radiative forcing, or energy absorption. About 80 percent of it comes from CO2. The EPA notes, however, that there are uncertainties and limitations in the models used to calculate radiative forcing.
Temperature: The past decade was the warmest on record worldwide. Average temperatures in the lower 48 states have risen an average 0.13 degrees Fahrenheit per decade since 1901.
Heat Waves: The frequency of heat waves and the percentage of the United States experiencing heat waves has increased since the 1970s, though the most severe years remain the Dust Bowl years of the 1930s.
Drought: Data on this indicator is relative new, so the EPA notes that it can't yet say whether droughts are increasing or decreasing over time.
Precipitation: Average rain and snowfall has increased in the U.S. at a rate of 6.4 percent per century since 1901, though conditions vary within regions. Parts of the Southwest, for example, have seen a decrease in precipitation.
Heavy Precipitation: Eight of the 10 worst years for downpours, or "intense single-day events," in the United States have been since 1990.
Tropical Cycle Intensity: Six of the 10 most active hurricane seasons have been since the mid-1990s.
Ocean Heat: Studies show an increase since the 1950s in heat stored, which effects sea surface temperature, sea levels and currents. EPA notes that the data interpretations vary as scientists are working with different measuring techniques.
Sea Surface Temperature: Temperatures rose an average of 0.12 degrees per decade from 1901 through 2009, with the fastest rise over the past 30 years.
Sea Level: On average, sea level has increased at a rate of six-tenths of an inch per decade since the 1870s.
Ocean Acidity: Oceans absorb CO2, and measurements over the past few decades show their acidity has increased, however the EPA says more research is needed to better understand long-term changes.
Arctic Sea Ice: In 2007, scientists recorded the smallest amount of sea ice on record.
Glaciers: Glaciers worldwide have lost more than 2,000 cubic miles of water since 1960.
Lake Ice: Northern U.S. lakes have stayed ice-free about one to two days longer each decade since the late 1800s.
Snow Cover: Averages by decade show the extent of North American snow cover has decreased steadily, from 3.4 million square miles in the 1970s to 3.18 million in the 2000s.
Snowpack: The depth of snow in early spring has, on average, decreased in the western U.S., with some areas seeing a decline of more than 75 percent between 1950 and 2000.
Heat-Related Deaths: Data classifying deaths as heat-related is relatively new, and the EPA notes there is considerable year-to-year variability in the number making it difficult to say if there has been a meaningful increase.
Length of Growing Season: Earlier spring warming and later fall frosts have increased the average length of the growing season in the lower 48 states by about two weeks since the start of the 20th century.
Plant Hardiness Zones: Warmer winter temperatures, noticeably since 1990, have shifted where species of plants are able to thrive.
Leaf and Bloom Dates: Leaves are emerging and lilacs an honeysuckle are blooming slightly earlier than in 1900, but the EPA notes that it's difficult to yet determine if this is statistically meaningful.
Bird Wintering Ranges: Studies have found birds in North America have shifted their wintering grounds an average of 35 miles northward over the past half century.