Hemispheric Temperature Change Northern Hemisphere 5 Yr Mean Southern Hemisphere 5 Yr Mean Temperature Anomaly °C 1880 1900 1920 1940 1960 1980 2000 Most climate scientists agree that Earth's climate is growing warmer They tell us that Earth's average temperature has risen by about 1 4 degrees Fahrenheit 0 8 degree Celsius since 1880 6
Cordilleran Ice Sheet Laurentide Ice Sheet FROZEN PLANET Earth’s climate has changed many times in the past Over the last two million years huge ice sheets have spread over the Earth and shrunk back several times Climate can change from natural events Earth’s climate can change from a large volcanic eruption for instance or from slight changes in the amount of energy from the sun Gases released from a volcanic eruption can change the climate 7
97 But most climate scientists agree that the current warming can not be explained by natural events alone Most of the warming of the last hundred years is very likely caused by the burning of fossil fuels OF CLIMATE PAPERS STATING A POSITION ON HUMAN CAUSED GLOBAL WARMING AGREE GLOBAL WARMING IS HAPPENING AND WE ARE THE CAUSE TheConsensus Project com the consensus project 8
Greenhouse Effect Solar Radiation Greenhouse Gases Greenhouse Effect Reflected Radiation When fossil fuels such as oil and coal are burned carbon dioxide goes into the air Carbon dioxide is a greenhouse gas That means it traps heat from the sun and prevents the heat from escaping into space EARTH’S THERMOSTAT In the 1850s Irish scientist John Tyndall discovered that nitrogen and oxygen in the atmosphere allow light and heat to pass freely Other gases like carbon dioxide and water vapor trap heat from the sun Tyndall realized that heat-trapping gases help set Earth’s temperature John Tyndall 1820 1893 9
