U.S National Climate Assessment Report

פורסם: 10 במאי 2014, 1:03 על ידי: Sustainability Org   [ עודכן 17 במאי 2014, 3:30 ]
In May 2014, the U.S. Global Change Research Program released the Third National Climate Assessment, the authoritative and comprehensive report on climate change and its impacts in the United States.

The National Climate Assessment summarizes the impacts of climate change on the United States, now and in the future. A team of more than 300 experts guided by a 60-member Federal Advisory Committee produced the report, which was extensively reviewed by the public and experts, including federal agencies and a panel of the National Academy of Sciences.

This report documents the changes already observed and those projected for the future.

It is important that these findings and response options be shared broadly to inform citizens and communities across our nation. Climate change presents a major challenge for society. This report advances our understanding of that challenge and the need for the American people to prepare for and respond to its far-reaching implications.

The cumulative weight of the scientific evidence contained in this report confirms that climate change is affecting the American people now, and that choices we make will affect our future and that of future generations.

Ten Indicators of a Warming World (press image to enlarge)

Projected Global Temperature Change


Different amounts of heat-trapping gases released into the atmosphere by human activities produce different projected increases in Earth’s temperature. In the figure, each line represents a central estimate of global average temperature rise (relative to the 1901-1960 average) for a specific emissions pathway. Shading indicates the range (5th to 95th percentile) of results from a suite of climate models. Projections in 2099 for additional emissions pathways are indicated by the bars to the right of each panel. In all cases, temperatures are expected to rise, although the difference between lower and higher emissions pathways is substantial. (Left) The panel shows the two main scenarios (SRES – Special Report on Emissions Scenarios) used in this report: A2 assumes continued increases in emissions throughout this century, and B1 assumes much slower increases in emissions beginning now and significant emissions reductions beginning around 2050, though not due explicitly to climate change policies. (Right) The panel shows newer analyses, which are results from the most recent generation of climate models (CMIP5) using the most recent emissions pathways (RCPs – Representative Concentration Pathways). Some of these new projections explicitly consider climate policies that would result in emissions reductions, which the SRES set did not.1,2 The newest set includes both lower and higher pathways than did the previous set. The lowest emissions pathway shown here, RCP 2.6, assumes immediate and rapid reductions in emissions and would result in about 2.5°F of warming in this century. The highest pathway, RCP 8.5, roughly similar to a continuation of the current path of global emissions increases, is projected to lead to more than 8°F warming by 2100, with a high-end possibility of more than 11°F. (Data from CMIP3, CMIP5, and NOAA NCDC).

Separating Human and Natural Influences on Climate


Observed global average changes (black line), model simulations using only changes in natural factors (solar and volcanic) in green, and model simulations with the addition of human-induced emissions (blue). Climate changes since 1950 cannot be explained by natural factors or variability, and can only be explained by human factors. (Figure source: adapted from Huber and Knutti).

As Oceans Absorb CO2 They Become More Acidic


The correlation between rising levels of CO2 in the atmosphere (red) at Mauna Loa and rising CO2 levels (blue) and falling pH (green) in the nearby ocean at Station Aloha. As CO2 accumulates in the ocean, the water becomes more acidic (the pH declines). (Figure source: modified from Feely et al. 2009).

Shells Dissolve in Acidified Ocean Water


Pteropods, or “sea butterflies,” are free-swimming sea snails about the size of a small pea. Pteropods are eaten by marine species ranging in size from tiny krill to whales and are an important source of food for North Pacific juvenile salmon. The photos above show what happens to a pteropod’s shell in seawater that is too acidic. The left panel shows a shell collected from a live pteropod from a region in the Southern Ocean where acidity is not too high. The shell on the right is from a pteropod collected in a region where the water is more acidic (Photo credits: (left) Bednaršek et al. 2012; (right) Nina Bednaršek).

human-induced changes in the global carbon dioxide budget


 Figure shows human-induced changes in the global carbon dioxide budget roughly since the beginning of the Industrial Revolution. Emissions from fossil fuel burning are the dominant cause of the steep rise shown here from 1850 to 2012. (Global Carbon Project 2010, 20121,2).

Response Options


Cities providing transportation options including bike lanes, buildings designed with energy saving features such as green roofs, and houses elevated to allow storm surges to pass underneath are among the many response options being pursued around the country.

John Sebastian Russo/San Francisco Chronicle/Corbis; Proehl Studios/Corbis; Courtesy of FEMA


The Highlights provides a concise version of the full report including an Overview, select evidence for the 12 Report Findings, and summaries of the impacts of climate change on every region of the United States.