Temperatures will continue to rise
Because human-induced warming is superimposed on a naturally varying climate, the temperature rise has not been, and will not be, uniform or smooth across the country or over time.
Frost-free season (and growing season) will lengthen
The length of the frost-free season (and the corresponding
growing season) has been increasing nationally since the
1980s, with the largest increases occurring in the western
United States, affecting ecosystems and agriculture. Across
the United States, the growing season is projected to
continue to lengthen.
Changes in precipitation patterns
Average U.S. precipitation has increased since 1900, but
some areas have had increases greater than the national
average, and some areas have had decreases. More winter and
spring precipitation is projected for the northern United
States, and less for the Southwest, over this century.
More droughts and heat waves
Droughts in the Southwest and heat waves (periods of
abnormally hot weather lasting days to weeks) everywhere
are projected to become more intense, and cold waves less
Hurricanes will become stronger and more intense
The intensity, frequency and duration of North Atlantic hurricanes, as well as the frequency of the strongest (Category 4 and 5) hurricanes, have all increased since the early 1980s. The relative contributions of human and natural causes to these increases are still uncertain. Hurricane-associated storm intensity and rainfall rates are projected to increase as the climate continues to warm.
Sea level will rise 1-4 feet by 2100
Global sea level has risen by about 8 inches since reliable
record keeping began in 1880. It is projected to rise
another 1 to 4 feet by 2100. This is the result of added
water from melting land ice and the expansion of seawater
as it warms.
Arctic likely to become ice-free
The Arctic Ocean is expected to become essentially ice free in summer before mid-century.
1. IPCC 2007, Summary for Policymakers, in Climate Change 2007: Impacts, Adaptation and Vulnerability. Contribution of Working Group II to the Fourth Assessment Report of the Intergovernmental Panel on Climate Change, Cambridge University Press, Cambridge, UK, p. 17.
2. USGCRP 2014, Third Climate Assessment .
U.S. regional effects
Below are some of the impacts that are currently visible throughout the U.S. and will continue to affect these regions, according to the Fourth National Climate Assessment Report 2, released by the U.S. Global Change Research Program :
Northeast. Heat waves, heavy downpours and sea level rise pose growing challenges to many aspects of life in the Northeast. Infrastructure, agriculture, fisheries and ecosystems will be increasingly compromised. Many states and cities are beginning to incorporate climate change into their planning. You can read more about impacts on New York State .
Northwest. Changes in the timing of stream flow reduce water supplies for competing demands. Sea level rise, erosion, inundation, risks to infrastructure and increasing ocean acidity pose major threats. Increasing wildfire, insect outbreaks and tree diseases are causing widespread tree die-off.
Southeast. Sea level rise poses widespread and continuing threats to the region’s economy and environment. Extreme heat will affect health, energy, agriculture and more. Decreased water availability will have economic and environmental impacts.
Midwest. Extreme heat, heavy downpours and flooding will affect infrastructure, health, agriculture, forestry, transportation, air and water quality, and more. Climate change will also exacerbate a range of risks to the Great Lakes.
Southwest. Increased heat, drought and insect outbreaks, all linked to climate change, have increased wildfires. Declining water supplies, reduced agricultural yields, health impacts in cities due to heat, and flooding and erosion in coastal areas are additional concerns.