Would that have been proof of global warming? No. Had the characters visited the nearby station of Santa Cruz Aeropuerto, the poster on the wall would have shown a positive trend. No one has or would claim that the whole globe is warming uniformly. Global warming is defined by the global mean surface temperature. “There’s your global warming,” one of Crichton’s good guys declares dismissively. In particular, characters visit Punta Arenas, at the tip of South America, where the station record posted on the wall shows a long-term cooling trend (though slight warming since the 1970s). The book also shows, through the selective use of weather-station data, a number of single-station records with long-term cooling trends.

Thus the conclusion that GHGs are driving warming. No model that does not include a sharp rise in greenhouse gases (GHGs), principally CO2, is able to match up with recent warming. Regional patterns of change appear to be linked more closely to internal variability, particularly during the 1930s. Our current “best guess” is that the global mean changes in temperature, including the 1940-1970 cooling, are quite closely related to the forcings. Even then, any discrepancy might be due to internal variability (related principally to the ocean on multi-decadal time scales). Matching up what really happened with what we might have expected to happen requires taking into consideration all the forcings, as best as we can.

Some forcings - sulfate and nitrate aerosols, land-use changes, solar irradiance, and volcanic aerosols, for instance - can cause cooling. In the real world, climate is affected both by internal variability (natural internal processes within the climate system) and forcings (external forces, either natural or human-induced, acting on the climate system). To support our nonprofit environmental journalism, please consider disabling your ad-blocker to allow ads on Grist.

The state of fear book