Evidence of Warming

Evidence of Warming

Global climate is warming. As the amount of carbon dioxide in the atmosphere has increased, global average temperatures have risen. The graphs below add some context to how these changes have occurred over the last couple of centuries.

Carbon Emissions

Total global carbon emissions (black line on the graph below) have increased since the start of the Industrial Revolution in the mid-nineteenth century. Coal (green line) was much more widely used during the first half of the 20th Century than petroleum or natural gas. It powered the many inventions developed at the time and it was widely used in furnaces to heat homes. Natural gas (red line) became more widely used after World War II when pipelines were built. The use of petroleum increased dramatically (blue line) after the discovery of enormous oil fields in the rocks under Saudi Arabia and Kuwait.


Carbon Dioxide Concentrations

Carbon dioxide concentrations (on the graph below) have increased since the start of the Industrial Revolution as more carbon has been emitted into the atmosphere. Note that the x-axis for this graph stretches back to 1750, a half century before the above. The data used to make this graph comes from four different ice cores (shown as blue, red, green, and black dots) and annual average direct measurements of CO2 in the atmosphere (blue line).

Global Average Temperature

Global average temperature has increased (graph below) as carbon dioxide and other heat-trapping greenhouse gases have been added to the atmosphere. During the 20th Century, global average temperate has increased 0.6 degrees Celsius (1.1 degrees Fahrenheit). Note that this graph starts at about 1855. This is as far back as we have good direct measurements of global temperature.


Change in temperature hasn't been the same everywhere.

While global average temperature has increased over the past century, the rate of warming has not been the same everywhere. The map below indicates that much of the high latitudes in the Northern Hemisphere and the Antarctic Peninsula have warmed more in recent decades than other places. This map shows recent changes in Earth's surface air temperatures. The colors indicate the temperatures in the decade around 2000 as compared to average values from about 40 years earlier. Specifically, the colors compare average temperatures during the years 1995 through 2004 versus the averages from 1940 through 1980. The global average temperature increased about 0.42° C during this time.


(Images: Robert A. Rohde, Global Warming Art Project)

© 2011