This graph, based on the comparison of atmospheric samples contained in ice cores and more recent direct measurements, provides evidence that atmospheric CO2 has increased since the Industrial Revolution. (Source: NOAA)

Resources The following are the key sources of data and information contained on this page: IPCC Fourth Assessment Report, Summary for Policymakers IPCC Fourth Assessment Report, Technical Summary NOAA Paleoclimatology

The Earth's climate has changed throughout history. Just in the last 650,000 years there have been seven cycles of glacial advance and retreat, with the abrupt end of the last ice age about seven thousand years ago, marking the beginning of the modern climate era —and of human civilization. Most of these changes are attributed to the very small changes in the Earth’s orbit changing the amount of solar energy the Earth receives.

"Scientific evidence for warming of the climate system is unequivocal."
- Intergovernmental Panel on Climate Change

The current warming trend is of particular significance because most of it is very likely human-induced and proceeding at a rate that is unprecedented in the past 1,300 years.¹

Earth-orbiting satellites and other technological advances have enabled scientists to see the big picture, collecting many different types of information about our planet and its climate on a global scale. Studying these climate data collected over many years reveal the signals of a changing climate.

Certain facts about Earths climate are not in dispute:

• The heat-trapping nature of carbon dioxide and other gases was demonstrated in the mid-19th century.² Their ability to affect the transfer of infrared energy through the atmosphere is the scientific basis of many JPL-designed instruments, such as AIRS. Increased levels of greenhouse gases must cause the Earth to warm in response.

• Ice cores drawn from Greenland, Antarctica, and tropical mountain glaciers show that the Earth’s climate responds to changes in solar output, in the Earth’s orbit, and in greenhouse gas levels. They also show that in the past, large changes in climate have happened very quickly, geologically-speaking: in tens of years, not in millions or even thousands.

The evidence for abrupt climate change is compelling:

Aitutaki atoll: Vulnerable to rising sea levels	Global sea level rose about 17 centimeters (6.7 inches) in the last century. The rate in the last decade, however, is nearly double that of the last century.3
The Keeling Curve shows a pattern of steadily increasing carbon dioxide in the atmosphere since 1958.	Levels of Carbon Dioxide are higher today than at anytime in past 650,000 years. Scientists reconstruct past climate conditions through evidence preserved in tree rings, coral reefs and ice cores. For example, ice cores removed from 2 miles deep in the Antarctic contain atmospheric samples trapped in tiny air bubbles that date as far back as 650,000 years. These samples have allowed scientists to construct a historical record of greenhouse gas concentration stretching back hundreds of thousands of years.
The effects of climate change will likely include more frequent droughts in some areas and heavier precipitation in others.	All three major global surface temperature reconstructions show that Earth has warmed since 1880. 4-6 Most of this warming has occurred since the 1970s, with the 20 warmest years having occurred since 1981 and with all 10 of the warmest years occurring in the past 12 years. 7 Even though the 2000s witnessed a solar output decline resulting in an unusually deep solar minimum in 2007-2009, surface temperatures continue to increase. 8-10
	The oceans have absorbed much of this increased heat, with the top 700 meters (about 2,300 feet) of ocean showing warming of 0.302 degrees Fahrenheit since 1969.11
Flowing meltwater from the Greenland ice sheet	The Greenland and Antarctic ice sheets have decreased in mass. Data from JPLs Gravity Recovery and Climate Experiment show Greenland lost 150 to 250 cubic kilometers (36 to 60 cubic miles) of ice per year between 2002 and 2006, while Antarctica lost about 152 cubic kilometers (36 cubic miles) of ice between 2002 and 2005.
The disappearing snowcap of Mount Kilimanjaro, from space.	Glaciers are retreating almost everywhere around the world — including in the Alps, Himalayas, Andes, Rockies, Alaska and Africa.12
	Precipitation and evaporation patterns over the oceans have changed, as evidenced by increased ocean salinity near the equator and decreased salinity at higher latitudes.13

¹³IPCC Assessment Report 4, Technical Summary, p. 48