Global climate change indicators monitoring references national centers for environmental information (ncei) gas kinetic energy

###

Thousands of land and ocean temperature measurements are recorded each day around the globe. This includes measurements from climate reference stations, weather stations, ships, buoys and autonomous gliders in the oceans. These surface measurements are also supplemented with satellite measurements. These measurements are processed, examined for random and systematic errors, and then finally combined to produce a time series of global average temperature change. A number of agencies around the world have produced datasets of global-scale changes in surface temperature using different techniques to process the data and remove measurement errors that could lead to false interpretations of temperature trends. The warming trend that is apparent in all of the independent methods of calculating global temperature change is also confirmed by other independent observations, such as the melting of mountain glaciers on every continent, reductions in the extent of snow cover, earlier blooming of plants in spring, a shorter ice season on lakes and rivers, ocean heat content, reduced arctic sea ice, and rising sea levels.

Global annual average temperature measured over land and oceans. Red bars indicate temperatures above and blue bars indicate temperatures below the 1901-2000 average temperature. The black line shows atmospheric carbon dioxide concentration in parts per million.

Global average temperature is one of the most-cited indicators of global climate change, and shows an increase of approximately 1.4°F since the early 20 th Century. The global surface temperature is based on air temperature data over land and sea-surface temperatures observed from ships, buoys and satellites. There is a clear long-term global warming trend, while each individual year does not always show a temperature increase relative to the previous year, and some years show greater changes than others. These year-to-year fluctuations in temperature are due to natural processes, such as the effects of El Ninos, La Ninas, and the eruption of large volcanoes. Notably, the 20 warmest years have all occurred since 1981, and the 10 warmest have all occurred in the past 12 years.

A large body of evidence supports the conclusion that human activity is the primary driver of recent warming. This evidence has accumulated over several decades, and from hundreds of studies. The first line of evidence is our basic physical understanding of how greenhouse gases trap heat, how the climate system responds to increases in greenhouse gases, and how other human and natural factors influence climate. The second line of evidence is from indirect estimates of climate changes over the last 1,000 to 2,000 years. These estimates are often obtained from living things and their remains (like tree rings and corals) which provide a natural archive of climate variations. These indicators show that the recent temperature rise is clearly unusual in at least the last 1,000 years. The third line of evidence is based on comparisons of actual climate with computer models of how we expect climate to behave under certain human influences. For example, when climate models are run with historical increases in greenhouse gases, they show gradual warming of the Earth and ocean surface, increases in ocean heat content, a rise in global sea level, and general retreat of sea ice and snow cover. These and other aspects of modeled climate change are in agreement with observations.

Carbon dioxide concentration (parts per million) for the last 800,000 years, measured from trapped bubbles of air in an Antarctic ice core. The 2008 observed value is from the Mauna Loa Observatory in Hawaii and projections are based upon future emission scenarios. More information on the data can be found in the Climate Change Impacts on the U.S. report.

Over the last 800,000 years, natural factors have caused the atmospheric carbon dioxide (CO 2) concentration to vary within a range of about 170 to 300 parts per million (ppm). The concentration of CO 2 in the atmosphere has increased by roughly 35 percent since the start of the industrial revolution. Globally, over the past several decades, about 80 percent of human-induced CO 2 emissions came from the burning of fossil fuels, while about 20 percent resulted from deforestation and associated agricultural practices. In the absence of strong control measures, emissions projected for this century would result in the CO 2 concentration increasing to a level that is roughly 2 to 3 times the highest level occurring over the glacial-interglacial era that spans the last 800,000 or more years.