|A relatively small shift in the mean produces a larger change in the number of extremes for both temperature and precipitation (top right, bottom right). Click to enlarge.|
The US Climate Change Science Program (CCSP) and the Subcommittee on Global Change Research has released a scientific synthesis and assessment report that provides the first comprehensive analysis of observed and projected changes in weather and climate extremes in North America and US territories.
Among the major findings reported in this assessment are that droughts, heavy downpours, excessive heat, and intense hurricanes are likely to become more commonplace as humans continue to increase the atmospheric concentrations of heat-trapping greenhouse gases.
Intergovernmental Panel on Climate Change (IPCC) previously evaluated extreme weather and climate events on a global basis in this same context. However, there has not been a specific assessment across North America prior to this report.
The report is based on scientific evidence that a warming world will be accompanied by changes in the intensity, duration, frequency, and geographic extent of weather and climate extremes.
Global warming of the past 50 years is due primarily to human-induced increases in heat-trapping gases, according to the report. Many types of extreme weather and climate event changes have been observed during this time period and continued changes are projected for this century. Specific future projections include:
Abnormally hot days and nights, along with heat waves, are very likely to become more common. Cold nights are very likely to become less common.
Sea ice extent is expected to continue to decrease and may even disappear in the Arctic Ocean in summer in coming decades.
Precipitation, on average, is likely to be less frequent but more intense.
Droughts are likely to become more frequent and severe in some regions.
Hurricanes will likely have increased precipitation and wind.
The strongest cold-season storms in the Atlantic and Pacific are likely to produce stronger winds and higher extreme wave heights.
The impacts of changes in extremes depend on both changes in climate and ecosystem and societal vulnerability. The degree of impacts are due, in large part, to the capacity of society to respond. Vulnerability is shaped by factors such as population dynamics and economic status as well as adaptation measures such as appropriate building codes, disaster preparedness, and water use efficiency. Some short-term actions taken to lessen the risk from extreme events can lead to increases in vulnerability to even larger extremes. For example, moderate flood control measures on a river can stimulate development in a now “safe” floodplain, only to see those new structures damaged when a very large flood occurs.—“Weather and Climate Extremes in a Changing Climate”
The CCSP also released another one of the 21 synthesis and assessment products in the series, this one a preliminary review of adaptation strategies for climate-sensitive ecosystems and resources.
This report finds that climate change can increase the impact of traditional stressors (such as pollution or habitat destruction) on ecosystems, and that many existing best management practices to reduce these stressors can also be applied to reduce the impacts of climate change.
For example, current efforts to reverse habitat destruction by restoring vegetation along streams also increase ecosystem resilience to climate change impacts, such as greater amounts of pollutants and sediments from more intense rainfall.
The CCSP was established in 2002 to provide science-based knowledge to manage the risks and opportunities of changes in the climate and related environmental systems. The program is responsible for coordinating and integrating the research of 13 federal agencies on climate and global change.
Weather and Climate Extremes in a Changing Climate Final Report, Synthesis and Assessment Product 3.3
Preliminary review of adaptation options for climate-sensitive ecosystems and resources Final Report, Synthesis and Assessment Product 4.4