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By the Numbers: Analyzing the U.S. National Climate Assessment

The draft U.S. National Climate Assessment was released last week, confirming that the climate is changing, that it is primarily due to human activities, and that the United States is already being adversely impacted. These top-line messages should come as no surprise, as they reconfirm the major findings of previous National Climate Assessments and of the Intergovernmental Panel on Climate Change’s recent reports.

But the 1,000-plus pages of the Assessment also carry important findings—many of which have not been highlighted in media reports thus far. WRI’s experts reviewed the assessment in its entirety. Below, we boil down some of the highlights from this comprehensive body of work, including its findings on how increases in greenhouse gas emissions have impacted temperature, sea level rise, precipitation, ice cover, ecosystems, and human health in the United States and globally.

Temperature

Build-up of greenhouse gases in the atmosphere has already caused America’s average temperature to rise by 1.5 ˚F since 1895, according to the assessment. With continued increases in emissions, U.S. temperatures are projected to increase 5-10˚F by the end of the century. Rising temperatures have implications for human health, drought, storm intensity, and species and ecosystem health, among others. A few other notable statistics include: * 0.5˚F: Temperature increase that would occur even if emissions were suddenly stopped

  • 2˚F: Temperature increase in the Northeast since 1895

  • Every 2-3 years: How often the United States will experience what is now a once-in-20-year heat wave by the end of the century

  • 3˚F: Rise in average temperature in Alaska since 1949

  • 3-6˚F: How high average temperature is projected to increase by 2080-2100 in the continental United States

  • 5˚F: Amount that the Atlantic Ocean was warmer than normal when Hurricane Sandy struck, increasing the storm’s strength

  • 5˚F: Average winter air temperature increase in Alaska over the past 60 years

  • 40: Consecutive days that Texans experienced 100+˚F temperature in 2011

Emissions

According to the report, the United States currently contributes 20 percent of global greenhouse gas emissions. Changes in temperature, precipitation, and sea level rise are in part dictated by the composition of greenhouse gases in the atmosphere. In addition, the oceans are becoming more acidic as carbon dioxide enters waters. Below are some of the figures related to greenhouse gas emissions:

  • 13%: Amount of carbon dioxide emissions associated with U.S. fossil fuel burning that are absorbed by forests

  • 16%: Amount of CO2 emissions stemming from land-related activities globally (the rest is due to fossil fuel burning)

  • 40%: Amount global atmospheric CO2 concentrations have increased above pre-industrial levels

  • 50%: Amount of global CO2 removed from the atmosphere during a century (the rest stays in the atmosphere for longer)

  • 0.9 billion: Number of tons that global greenhouse gas emissions have been rising per year over the last decade

  • 37 billion: Tons of greenhouse gases emitted globally in 2011

  • 530 billion: Tons of CO2 that the oceans have absorbed over the last 250 years

Sea Level Rise

The report shows that seas have risen by 8 inches globally since 1880, threatening coastal populations, livelihoods, and industry. A few other notable stats include:

  • 1 foot: Increase in coastal flooding in the Northeast due to sea level rise since 1900

  • 1-4 feet: Projected amount of sea level rise for the world’s oceans by 2100

  • 5 million: People in the United States who live within 4 feet of the local high-tide line

Precipitation

The annual average precipitation across the continental United States has increased by 2 inches since 1895. In addition to changes in average precipitation, the precipitation associated with extreme weather events has increased, showcasing climate change’s impacts on more volatile and unpredictable weather patterns. Some other figures include:

  • 5 inches: Increase in precipitation in the Northeast since 1895

  • 5%: Increase of average annual precipitation in the United States since 1900

  • 74%: Increase in the amount of precipitation associated with very heavy, extreme precipitation events in the Northeast between 1958 and 2010

  • $5 billion: Monetary losses associated with impacted livestock and crops during the 2011 drought in Texas. In another report released last year, scientists from NOAA, the U.K.'s Met Office, and other institutions showed that the conditions leading to the 2011 Texas drought are 20 times more likely to occur now than in the 1960s as a result of rising greenhouse gas emissions and associated climatic changes .

Ice

Disturbingly, the report found that, assuming continued growth in global emissions, there will be no summer sea ice in the Arctic left by mid-century. This ice melt can have ripple effects not only across ecosystems, but weather systems, livelihoods, and transportation. Other statistics include:

  • 40%: Decrease in minimum Arctic sea ice extent since satellite records began in 1978

  • 63%: Decrease in total winter ice coverage in the Great Lakes since the early 1970s

Ecosystems

Anywhere from 5 to 20 percent of land area in the United States could be subject to ecosystem changes by 2100 as a result of climate change, the draft report shows. That’s problematic because, in addition to supporting communities, livelihoods, and wildlife, ecosystems play a key role in stabilizing the climate. In addition, efforts to mitigate climate change and changes to the U.S. energy system have altered landscapes to accommodate new fuels. Below are some other statistics from the draft report with regard to ecosystems, the U.S. energy system, and climate change:

  • 10: Number of days that bees have advanced their arrival in the spring in the northeastern United States over the past 130 years

  • 10.5: Average miles per decade that plants and animals have migrated to higher latitudes to find suitable habitats

  • 40%: Amount of 2011 U.S. corn crop used to produce ethanol, which met 10 percent of U.S. gasoline demand

  • 48%: Amount of U.S. trout species in the western United States projected to be lost by 2080 as a result of changes in temperature and precipitation

  • 75%: Amount of world’s coral reefs that are threatened by climate change and other stressors

  • 9.2 million: Acres burned in the United States during the 2012 wildfire season

  • $3.6 - 6.1 billion: Amount of money permafrost thaw could add to infrastructure maintenance costs over the next two decades

Health

Pollution, weather changes, droughts, fires, heat waves, and other climate change impacts can wreak havoc on human health and have attendant impacts to our economy. As the draft assessment shows, human health in the United States has already been affected, and impacts will increase with every rise in temperature.

  • 13 -27: Days ragweed pollen season length has extended in some parts of the United States since 1995

  • 1,000: Premature deaths per 1.8°F rise in temperature, related to worsened ozone and particle pollution

  • $6.5 billion: Cost associated with the health impacts of climate change’s current effects on ozone

Two hundred and forty experts came together to review the latest scientific literature to compile the Assessment. The report is the third National Climate Assessment conducted, adding to a growing evidence base showcasing humanity’s role in global climate change.

While the numbers presented above are of critical importance, the most important ones are these:

  • 100%: Amount of people who will be affected by climate change

  • 100%: Amount of people who will need to play a role in reversing our carbon-intensive ways if we are to change the statistics presented in this report

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