Evidence for climate change abounds, from the top of the atmosphere to the depths of the oceans. 18 This evidence has been compiled by scientists and engineers from around the world, using 19 satellites, weather balloons, thermometers, buoys, and other observing systems. The sum total of 20 this evidence tells an unambiguous story: the planet is warming.
1. Global climate is changing, and this is apparent across the U.S. in a wide range of 3 observations. The climate change of the past 50 years is due primarily to human activities, 4 predominantly the burning of fossil fuels.
2. Some extreme weather and climate events have increased in recent decades, and there is
new and stronger evidence that many of these increases are related to human activities.
3. Human-induced climate change is projected to continue and accelerate significantly if emissions of heat-trapping gases continue to increase.
4. Impacts related to climate change are already evident in many sectors and are expected to become increasingly challenging across the nation throughout this century and beyond.
5. Climate change threatens human health and well-being in many ways, including impacts from increased extreme weather events, wildfire, decreased air quality, diseases
transmitted by insects, food, and water, and threats to mental health.
6. Infrastructure across the U.S. is being adversely affected by phenomena associated with
climate change, including sea level rise, storm surge, heavy downpours, and extreme
7. Reliability of water supplies is being reduced by climate change in a variety of ways that
affect ecosystems and livelihoods in many regions, particularly the Southwest, the Great
Plains, the Southeast, and the islands of the Caribbean and the Pacific, including the state
8. Adverse impacts to crops and livestock over the next 100 years are expected. Over the
next 25 years or so, the agriculture sector is projected to be relatively resilient, even
though there will be increasing disruptions from extreme heat, drought, and heavy
downpours. U.S. food security and farm incomes will also depend on how agricultural
systems adapt to climate changes in other regions of the world.
9. Natural ecosystems are being directly affected by climate change, including changes in
biodiversity and location of species. As a result, the capacity of ecosystems to moderate
the consequences of disturbances such as droughts, floods, and severe storms is being
10. Life in the oceans is changing as ocean waters become warmer and more acidic.
11. Planning for adaptation (to address and prepare for impacts) and mitigation (to reduce
emissions) is increasing, but progress with implementation is limited.
1.Northeast- Heat waves, coastal flooding due to sea level rise and storm surge, and river flooding due to more extreme precipitation events are affecting communities in the region.
2. Southeast- Decreased water availability, exacerbated by population growth and landuse change, is causing increased competition for water; risks associated with extreme events like hurricanes are increasing. Midwest Longer growing seasons and rising carbon dioxide levels are increasing yields of some crops, although these benefits have already been offset in some instances by occurrence of extreme events such as heat waves, droughts, and floods.
3. Great Plains- Rising temperatures are leading to increased demand for water and energy and impacts on agricultural practices.
4. Southwest- Drought and increased warming have fostered wildfires and increased competition for scarce water resources for people and ecosystems.
5. Northwest- Changes in the timing of streamflow related to earlier snowmelt have already been observed and are reducing the supply of water in summer, causing far-reaching ecological and socioeconomic consequences.
6. Alaska- Summer sea ice is receding rapidly, glaciers are shrinking, and permafrost is thawing, causing damage to infrastructure and major changes to ecosystems; impacts to Alaska native communities are increasing.
7. Hawaii- Increasingly constrained freshwater supplies, coupled with increased temperatures, are stressing both people and ecosystems, and decreasing food and water security.
8. Coasts- Coastal lifelines, such as water supply infrastructure and evacuation routes, are increasingly vulnerable to higher sea levels and storm surges, inland flooding, and other climate-related changes.
9. Oceans- The oceans are currently absorbing about a quarter of human-caused carbon dioxide emissions to the atmosphere and over 90% of the heat associated with global warming, leading to ocean acidification and the alteration of marine ecosystems.
The most recent solar minimum occurred in 2008, and the sun began to ramp up in January 2010, with an M-class flare (a flare that is 10 times less powerful than the largest flares, labeled X-class). The sun has continued to get more active, with the next solar maximum predicted for 2013.
Floods along the nation’s rivers, inside cities, and on lakes following heavy downpours, prolonged rains, and rapid melting of snowpack are damaging infrastructure in towns and cities, farmlands, and a variety of other places across the nation.
The coterminous US is divided into four large regions and stationary bootstrapping is used to evaluate if the patterns of these statistical associations are significantly different from what would be expected under the null hypothesis that flood magnitudes are independent of GM [global mean] CO2. In none of the four regions defined in this study is there strong statistical evidence for flood magnitudes increasing with increasing GMCO2.
There is limited to medium evidence available to assess climate-driven observed changes in the magnitude and frequency of floods at regional scales because the available instrumental records of floods at gauge stations are limited in space and time, and because of confounding effects of changes in land use and engineering. Furthermore, there is low agreement in this evidence, and thus overall low confidence at the global scale regarding even the sign of these changes.
There continues to be a lack of evidence regarding the sign of trend in the magnitude and/or frequency of floods on a global scale
Observations to date provide no conclusive and general proof as to how climate change affects flood behaviour