“Global warming is closely associated with a broad spectrum of other changes, such as increases in the frequency of intense rainfall, decreases in Northern Hemisphere snow cover and Arctic sea ice, warmer and more frequent hot days and nights, rising sea levels, and widespread ocean acidification."
-National Research Council, 2010

Global Average Temperature Has Been Rising

Global average temperature has increased during the 20th Century, with the greatest warming over land areas and the Arctic.

The following video shows global surface temperatures, 1881-2009. The most recent decade was the warmest in the past century. Red indicates temperatures that are warmer and blue indicates temperatures cooler than the long-term average.

Obtained from NASA/Goddard Space Flight Center Scientific Visualization Studio Data, provided by Robert B. Schmunk (NASA/GSFC GISS)

Heat Waves Have Been More Frequent

Heat waves have become more frequent in recent decades. They are the leading cause of weather-related morbidity and mortality in the United States.

Statistics show a general trend towards increased frequency and intensity of heat wave events.


The number of reported heat wave events worldwide has been increasing, as shown on this graph.

Graph derived from EM-DAT, The International Disaster Database, Centre for Research on the Epidemiology of Disasters (CRED;, Université Catholique de Louvain, Brussels, Belgium, v12.07.



Heat waves are often compounded by poor air quality. They pose the greatest threat to vulnerable populations such as the elderly and children.


Drought Has Been More Frequent Globally

Globally, the areas affected by drought have more than doubled since the 1970s.

This sequence shows the decline of Africa's Lake Chad over the 1963 to 1997 period. Due to persistent drought and increasing water demand, it is now one-tenth its former size.


Lake Chad

Sea Levels Have Been Rising

Sea level has increased along most of the U.S. coast over the past 50 years, with some areas along the Atlantic and Gulf coasts experiencing increases of greater than 8 inches (20 cm).

Average sea level has been rising and is projected to continue to rise. Sea level rises due to ocean warming, which causes water to expand, and glacier and ice sheet to melting. 

Data from Church, J. and N. White (2011), Sea-level rise from the late 19th to the early 21st century. Surveys in geophysics, 1573-0956. DOI: 10.1007/s10712-011-9119-1.


Average sea level rise is projected to rise 1.6-3.3 feet (0.5-1.0 m) by 2100. Some studies suggest a rise of nearly 6 ft (nearly 2 m). The following maps show how sea level rise would affect Delaware and Florida.


(dark blue areas indicate flooded land)

(royal blue areas indicate flooded land)

0ft (0 m)

1.6 ft (0.5 m)

3.3 ft (1 m)

4.9 ft (1.5 m)

6.6 ft (2 m)


Arctic Ice Sheets Have Been Shrinking

In Greenland, ice sheet melt has increased 30 percent over the past 30 years.

This animation depicts changes in the Greenland Ice Sheet mass, 2003-2009. Overall, ice mass is decreasing. Cool colors indicate ice mass decreases. Beiges indicate increases. Most ice is lost from Greenland’s edges.

Alpine Glaciers Have Been Receding

Nearly all of the world’s glacier systems have been shrinking, and in many cases their rate of ice loss has been accelerating.

Glaciers are melting in many parts of the world. The following pictures show how melting has affected two Alaskan glaciers.

Photos of Toboggan Glacier, Prince William Sound, Alaska


Source: USGS


Source: USGS


Photos of Plateau Glacier, Saint Elias Mountains, Alaska


Source: USGS


Source: USGS


This graph shows the decrease in global glacier volume since 1960.

Source: USGCRP (2009)

Heavy Precipitation Events Have Been More Frequent

Globally, precipitation has increased and the percentage of precipitation falling in the form of heavy rain events has also increased.

As illustrated in these graphs, extreme rainfall events have grown more common and their frequency is likely to increase as the planet warms further.

U.S. heavy precipitation events have increased over the 20th century. This graph shows the increase in 1-in-20 year precipitation events.

Graph provided by Dr. Kenneth Kunkel at the Cooperative Institute for Climate and Satellites (CICS-NC), North Carolina State University and NOAA's National Climatic Data Center, Asheville, NC

This graph shows projected changes in light, moderate, and heavy precipitation in North America for the 21st century. Light precipitation is projected to decrease, while heavy precipitation is projected to increase, continuing observed trends.

Arctic Sea Ice Has Been Declining

The average thickness of sea ice in the Arctic Ocean has declined substantially over the past half-century.

This NASA visualization shows Arctic Sea Ice Yearly Minimums from 1979 to 2010. In 2007, sea ice in the Arctic reached its lowest extent on record. 

Obtained from Lori Perkins at NASA/Goddard Space Flight Center Scientific Visualization Studio with data provided by Rob Gerston.

Oceans Have Been Increasing in Acidity

The average acidity of ocean surface waters has increased by a rate that exceeds any known rate of change in ocean acidity for at least 800,000 years.

Ocean acidity has increased roughly 30% since preindustrial times. Rising ocean acidity poses major risks for the shells of marine organisms such as swimming sea snails and phytoplankton, shown here. 

Image of a healthy Limacina helicinaLimacina are swimming sea snails that form an important component of marine food webs but are threatened by ocean acidification.

Photo by Russell Hopcroft, University of Alaska Fairbanks (UAF) and Census of Marine Life (CoML)

Image of a healthy Limacina retroversa.  Limacina are swimming sea snails that form an important component of marine food webs but are threatened by ocean acidification.

Photo by Russell Hopcroft, University of Alaska Fairbanks (UAF) and Census of Marine Life (CoML)

Phytoplankton are microscopic plant-like organisms vital to marine life. This is a scanning electron microscope (SEM) image of phytoplankton living in sea water with normal levels of acidity.

Photo credit: Ulf Riebesell, IFM-GEOMAR

These phytoplankton have become deformed from being placed in sea water with the levels of ocean acidity projected for 2100. The acid erodes the calcium carbonate shells of these organisms.

Photo credit: Ulf Riebesell, IFM-GEOMAR

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