Measuring Global Warming

GOES Weather Satellite

Broadcasters use data from meteorological satellites to predict weather and to broadcast storm warnings when necessary. Satellites such as the Geostationary Operational Environmental Satellite (GOES) collect meteorological and infrared information about the atmosphere and the ocean. A camera on the GOES is continuously pointed at Earth, broadcasting satellite images of cloud patterns both day and night. Here, the GOES-C satellite is being encapsulated inside its payload fairing aboard a Delta rocket.

     As early as 1896 scientists suggested that burning fossil fuels might change the composition of the atmosphere and that an increase in global average temperature might result. The first part of this hypothesis was confirmed in 1957, when researchers working in the global research program called the International Geophysical Year sampled the atmosphere from the top of the Hawaiian volcano Mauna Loa. Their instruments indicated that carbon dioxide concentration was indeed rising. Since then, the composition of the atmosphere has been carefully tracked. The data collected show undeniably that the concentrations of greenhouse gases in the atmosphere are increasing.

   Measuring warming of the global climate (the long-term average pattern of temperature) is a complex process. Temperatures vary widely all the time and from place to place, and a local warming trend may simply be due to the natural variability of the climate. But using many years of climate observations from around the world, scientists have detected a warming trend beyond such random fluctuations.

     Records going back to the late 1800s show a warming trend, but these statistics were spotty and untrustworthy. However, since 1957 data have been gathered from more reliable weather stations, located far away from cities, and since 1979 from satellites. These data have provided new, more accurate measurements, especially for the 70 percent of the planetary surface that is ocean water. These more accurate records indicate that a clear surface warming trend exists and that temperatures have risen particularly sharply in the last few decades.

     Eleven out of the twelve warmest years on record have occurred since 1995, with 2001-2006 all in the top six. Not every place in the world is warming at the same rate, or even warming at all—in fact, some parts of the world cooled over the 20th century. For this reason, many scientists use the term climate change rather than global warming. However, taking all of the local measurements together, the world is warming significantly, and many more places are warming than are cooling.