Vital Signs Of Global Warming

Carbon Dioxide

Carbon dioxide (CO2) is an important heat-trapping (greenhouse) gas, which is released through human activities such as deforestation and burning fossil fuels, as well as natural processes such as respiration and volcanic eruptions. The first chart shows atmospheric CO2 levels in recent years, corrected for average seasonal cycles. The second chart shows CO2 levels during the last three glacial cycles, as reconstructed from ice cores.

Global Temperature

The 10 warmest years in the 134-year record all have occurred since 2000, with the exception of 1998. The year 2014 ranks as the warmest on record. (Source: NASA/GISS). This research is broadly consistent with similar constructions prepared by the Climatic Research Unit and the National Atmospheric and Oceanic Administration.

Arctic Sea Ice Minimum

Arctic sea ice reaches its minimum each September. September Arctic sea ice is now declining at a rate of 13.3 percent per decade, relative to the 1981 to 2010 average.

Land Ice

Data from NASA's Grace satellites show that the land ice sheets in both Antarctica and Greenland are losing mass. The continent of Antarctica has been losing about 147 billion tons of ice per year since 2003, while the Greenland ice sheet has been losing an estimated 258 billion tons per year.

Sea Level

Sea level rise is caused primarily by two factors related to global warming: the added water coming from the melting of land ice and the expansion of sea water as it warms. The first chart tracks the change in sea level since 1993 as observed by satellites.

Forest Cover

Global forest loss between the years 2000 and 2012 was 888,000 square miles (2.3 million square kilometers), while 309,000 square miles (800,000 square kilometers) regrew during that period, according to a study using NASA/USGS Landsat 7 satellite data.

Of all countries globally, Indonesia exhibited the largest increase in forest loss during this period. Brazil exhibited the largest decline in annual forest loss, confirming reported reductions in forest clearing in the past decade. The causes of this loss include deforestation, wildfires, windstorms and insects. (Data for 2013 will be available soon.)