Culminating five years of work, the U.S. National Climate Assessment was released this morning, offering a comprehensive review of observed and projected climate change. The amount of information contained within the report is vast, but below are some of the key images from its highlight document. They reveal a world and nation warming, poised to warm more, and the impacts playing out before our eyes.
News story: U.S. climate report says global warming impact already severe
1. The period from 2001-2012 was the warmest on record globally. Every year was warmer than the 1990s average.
Via the report: “Bars show the difference between each decade’s average temperature and the overall average for 1901-2000.” (U.S. Global Change Research Program)
2. The warming trend is unlikely due to changes in the sun’s output, which has not varied substantially as temperatures have risen.
Via the report: “The full record of satellite measurements of the sun’s energy received at the top of the Earth’s atmosphere is shown in red, following its natural 11-year cycle of small ups and downs, without any net increase. Over the same period, global temperature relative to 1961-1990 average (shown in blue) has risen markedly. This is a clear indication that changes in the sun are not responsible for the observed warming over recent decades.” (U.S. Global Change Research Program)
3. U.S. temperatures have warmed 1.3-1.9 degrees since 1895, with most of the increase since 1970.
Via the report: “The colors on the map show temperature changes over the past 22 years (1991-2012) compared to the 1901-1960 average for the contiguous U.S., and to the 1951-1980 average for Alaska and Hawai’i. The bars on the graph show the average temperature changes by decade for 1901-2012 (relative to the 1901-1960 average). The far right bar (2000s decade) includes 2011 and 2012. The period from 2001 to 2012 was warmer than any previous decade in every region.” (U.S. Global Change Research Program)
4. Precipitation events are trending heavier in the U.S.
Via the report: “One measure of a heavy precipitation event is a 2-day precipitation total that is exceeded on average only once in a five-year period, also known as a once-in-five-year event. As this extreme precipitation index for 1901-2012 shows, the occurrence of such events has become much more common in recent decades. Changes are compared to the period 1901-1960, and do not include Alaska or Hawai‘i. The 2000s decade (far right bar) includes 2001-2012.” (U.S. Global Change Research Program)
5. Sea levels are rising, with some of the fastest rates (1-2 feet per century) in the Northeast.
Via the report: “The map on the left shows local sea level trends in the Northeast region. The length of the arrows varies with the length of the time series for each tide gauge location. The graph at the right shows observed sea level rise in Philadelphia, which has increased by 1.2 feet over the past century, significantly exceeding the global average of 8 inches, increasing the risk of impacts to critical urban infrastructure in low-lying areas.(U.S. Global Change Research Program)
6. Warmer ocean temperatures are leading to an increase in coral bleaching in tropical areas, in the U.S. and around the world.
Via the report: ” The global extent and severity of mass coral bleaching have increased worldwide over the last decade. Red dots indicate severe bleaching.” (U.S. Global Change Research Program)
7. The length of the frost-free season is growing.
Via the report: “The frost-free season length, defined as the period between the last occurrence of 32°F in the spring and the first occurrence of 32°F in the fall, has increased in each U.S. region during 1991-2012 relative to 1901-1960. Increases in frost-free season length correspond to similar increases in growing season length.” (U.S. Global Change Research Program)
8. The ragweed (pollen) season is expanding
Via the report: “Ragweed pollen season length has increased in central North America between 1995 and 2011 by as much as 11 to 27 days in parts of the U.S. and Canada in response to rising temperatures. Increases in the length of this allergenic pollen season are correlated with increases in the number of days before the first frost. As shown in the figure, the largest increases have been observed in northern cities.” (U.S. Global Change Research Program)
9. Heating demand is decreasing, cooling demand is increasing.
Via the report: “Figure shows observed increases in population-weighted cooling degree days, which result in increased air conditioning use, and decreases in population-weighted heating degree days, meaning less energy required to heat buildings in winter, compared to the average for 1970-2000. Cooling degree days are defined as the number of degrees that a day’s average temperature is above 65ºF, while heating degree days are the number of degrees a day’s average temperature is below 65ºF.” (U.S. Global Change Research Program)
10. Temperatures are projected to warm from a few to over 10 degrees by the end of the 21st century, depending on future greenhouse gas emissions.
Via the report: “Maps show projected change in average surface air temperature in the later part of this century (2071-2099) relative to the later part of the last century (1970-1999) under a scenario that assumes substantial reductions in heat trapping gases (B1) and a higher emissions scenario that assumes continued increases in global emissions (A2). These scenarios are used throughout this report for assessing impacts under lower and higher emissions.” (U.S. Global Change Research Program)
11. The hottest days are projected to warm substantially.
Via the report: “The maps show projected increases in the average temperature on the hottest days by late this century (2081-2100) relative to 1986-2005 under a scenario that assumes a rapid reduction in heat-trapping gases (RCP 2.6) and a scenario that assumes continued increases in these gases (RCP 8.5). The hottest days are those so hot they occur only once in 20 years. Across most of the continental U.S., those days will be about 10ºF to 15ºF hotter in the future under the higher emissions scenario, increasing health risks.” (U.S. Global Change Research Program)
12. Sea levels in the U.S. are projected to rise 1 to 4 feet depending on future greenhouse gas emissions and the rate of climate change
Via the report: “Figure shows estimated, observed, and possible amounts of global sea level rise from 1800 to 2100, relative to the year 2000. Estimates from proxy data (for example, based on sediment records) are shown in red (1800-1890, pink band shows uncertainty), tide gauge data in blue for 1880-2009, and satellite observations are shown in green from 1993 to 2012. The future scenarios range from 0.66 feet to 6.6 feet in 2100. These scenarios are not based on climate model simulations, but rather reflect the range of possible scenarios based on other kinds of scientific studies. The orange line at right shows the currently projected range of sea level rise of 1 to 4 feet by 2100, which falls within the larger risk-based scenario range. The large projected range reflects uncertainty about how glaciers and ice sheets will react to the warming ocean, the warming atmosphere, and changing winds and currents. As seen in the observations, there are year-to-year variations in the trend.” (U.S. Global Change Research Program)
13. Warming is projected to reduce soil moisture in much of the West by several to 10-15 percent by the end of the century; how fast and how much depends on future greenhouse gas emissions
Via the report: “Increased temperatures and changing precipitation patterns will alter soil moisture, which is important for agriculture and ecosystems and has many societal implications. These maps show average change in soil moisture compared to 1971-2000, as projected for late this century (2071-2100) under two emissions scenarios, a lower scenario (B1) and a higher scenario (A2). Eastern U.S. is not displayed because model simulations were only run for the area shown.” (U.S. Global Change Research Program)
14. The projected increase in the frost-free season, days without precipitation and hot nights will impact agriculture.
Via the report: “Many climate variables affect agriculture. The maps above show projected changes in key climate variables affecting agricultural productivity for the end of the century (2070-2099) compared to 1971-2000. Changes in climate parameters critical to agriculture show lengthening of the frost-free or growing season and reductions in the number of frost days (days with minimum temperatures below freezing), under an emissions scenario that assumes continued increases in heat-trapping gases (A2). Changes in these two variables are not identical, with the length of the growing season increasing across most of the United States and more variation in the change in the number of frost days. Warmer-season crops, such as melons, would grow better in warmer areas, while other crops, such as cereals, would grow more quickly, meaning less time for the grain itself to mature, reducing productivity.1 Taking advantage of the increasing length of the growing season and changing planting dates could allow planting of more diverse crop rotations, which can be an effective adaptation strategy. On the frost-free map, white areas are projected to experience no freezes for 2070-2099, and gray areas are projected to experience more than 10 frost-free years during the same period. In the lower left graph, consecutive dry days are defined as the annual maximum number of consecutive days with less than 0.01 inches of precipitation. In the lower right graph, hot nights are defined as nights with a minimum temperature higher than 98% of the minimum temperatures between 1971 and 2000.” (U.S. Global Change Research Program)
15. Climate change significantly increases the risk of water supply stress by mid-century, especially in the western U.S.
Via the report: “The effects of climate change, primarily associated with increasing temperatures and potential evapotranspiration, are projected to significantly increase water demand across most of the United States. Maps show percent change from 2005 to 2060 in projected demand for water assuming (a) change in population and socioeconomic conditions consistent with the A1B emissions scenario (increasing emissions through the middle of this century, with gradual reductions thereafter), but with no change in climate, and (b) combined changes in population, socioeconomic conditions, and climate according to the A1B emissions scenario.” (U.S. Global Change Research Program)
Much more information is available on the report’s gateway Web site, which contains widely accessible, sharable, and highly interactive climate information: nca2014.globalchange.gov