D.C. Watch

“Global Cooling” Skeptics Shield from Global Warming

Last night, my wife asked me if “Global Warming” was just like the “Global Cooling” hype of the 70’s, a trend that would die eventually? I could not answer that question for two reasons, 1) I was way to young to remember the 70s hype 2) I did not know the answer with absolute surety.

So I took on the task of researching these two topics, to my surprise the answers were astonishingly simple. (Click to Enlarge Images)

The 70’s were a time when issues like smog, particulate pollution, and acid rain were the focus of public concern (never really figured out why acid rain did not burn down the Amazon? but anyway), Carbon Dioxide was not such a big deal after all. While the press was hot on Global Cooling, among others, a notable theory suggested that the cooling effect was resultant of increased Aerosols in the atmosphere; a combustion by-product of… you guessed it “fossil fuel”. But in hindsight, what really happened between mid 1950’s and 1970 was in fact a slump in the rise of ground temperature, and came into attention only because of the unusually high temperature experienced between 1905 and 1955, the period preceding the slowdown. (Click to Enlarge Image)

A Newsweek article in 1975 pointed to “a drop of half a degree [Fahrenheit] in average ground temperatures in the Northern Hemisphere between 1945 and 1968. (Click to Enlarge Image) And rather than proposing environmentalist solutions, the Newsweek article suggested that “simple measures of stockpiling food or of introducing the variables of climatic uncertainty into economic projections of future food supplies” would be appropriate. The 70’s ended with many books of prophecies predicting the catastrophic return of the “Ice Age”.

Global Warming can be summarized with this scientific consensus, the average global temperature has risen 0.6 ± 0.2 °C over the 20th century, and that it is very likely attributable to human activities. (Click to Enlarge Image) And then there are the critics, some more wacky that others, even the US President joined in the bandwagon of skeptics and said this in a recent press conference when asked about his 2000 presidential election rival Al Gore’s movie, Mr. Bush said “And in my judgment, we need to set aside whether or not greenhouse gases have been caused by mankind or because of natural effects, and focus on the technologies that will enable us to live better lives and, at the same time, protect the environment.” Mr. President, with all due respect, Global Warming is caused by humans, and if you need proof, this link might help you understand it better, even they say that the “world’s leading climate scientists think that things people do are helping to make the Earth warmer”. Since you are not a scientist, the least you could do is pay heed.

United Nations created the Intergovernmental Panel on Climate Change (IPCC) to address whether or not global warming was anthropogenic. The result was the Kyoto Protocol. The IPCC in its Second Assessment Report (SAR) said that the “balance of evidence suggests that there is a discernible human influence on global climate” and strengthened this in its Third Assessment Report (TAR) in 2001 to, “There is new and stronger evidence that most of the warming observed over the last 50 years is attributable to human activities.”   Here are the major conclusions from their findings:

There is a longer and more closely scrutinised temperature record and new model estimates of variability. The warming over the past 100 years is very unlikely7 to be due to internal variability alone, as estimated by current models. Reconstructions of climate data for the past 1,000 years (Figure 1b) also indicate that this warming was unusual and is unlikely7 to be entirely natural in origin. 

 

There are new estimates of the climate response to natural and anthropogenic forcing, and new detection techniques have been applied. Detection and attribution studies consistently find evidence for an anthropogenic signal in the climate record of the last 35 to 50 years.

 

Simulations of the response to natural forcings alone (i.e., the response to variability in solar irradiance and volcanic eruptions) do not explain the warming in the second half of the 20th century (see for example Figure 4a). However, they indicate that natural forcings may have contributed to the observed warming in the first half of the 20th century.

 

The warming over the last 50 years due to anthropogenic greenhouse gases can be identified despite uncertainties in forcing due to anthropogenic sulphate aerosol and natural factors (volcanoes and solar irradiance). The anthropogenic sulphate aerosol forcing, while uncertain, is negative over this period and therefore cannot explain the warming. Changes in natural forcing during most of this period are also estimated to be negative and are unlikely7 to explain the warming.

 

Detection and attribution studies comparing model simulated changes with the observed record can now take into account uncertainty in the magnitude of modelled response to external forcing, in particular that due to uncertainty in climate sensitivity.

 

Most of these studies find that, over the last 50 years, the estimated rate and magnitude of warming due to increasing concentrations of greenhouse gases alone are comparable with, or larger than, the observed warming. Furthermore, most model estimates that take into account both greenhouse gases and sulphate aerosols are consistent with observations over this period.

 

The best agreement between model simulations and observations over the last 140 years has been found when all the above anthropogenic and natural forcing factors are combined, as shown in Figure 4c). . These results show that the forcings included are sufficient to explain the observed changes, but do not exclude the possibility that other forcings may also have contributed.

 

In the light of new evidence and taking into account the remaining uncertainties, most of the observed warming over the last 50 years is likely7 to have been due to the increase in greenhouse gas concentrations.

 

Furthermore, it is very likely7 that the 20th century warming has contributed significantly to the observed sea level rise, through thermal expansion of sea water and widespread loss of land ice. Within present uncertainties, observations and models are both consistent with a lack of significant acceleration of sea level rise during the 20th century.

 

Source: IPCC

With that said, the concerns of Global Cooling is far from over, the possible cooling effects of a slowdown or shutdown of the thermohaline circulation, which might be provoked by an increase of fresh water mixing into the North Atlantic due to glacial melting is a prevalent issue. If that is not enough, there are articles like this one in the Moscow News that does not warrant my comment.

Footnote: The Intergovernmental Panel on Climate Change (IPCC) has been established by WMO and UNEP to assess scientific, technical and socio- economic information relevant for the understanding of climate change, its potential impacts and options for adaptation and mitigation. It is open to all Members of the UN and of WMO.

Photo Courtesy: Wikipedia

 

Tags: global cooling, global warming, al gore, bush, US, IPCC, EPA

Posted by Moderator on June 1st, 2006 filed in Al Gore, Bush, EPA, Global Cooling, Global Warming, IPCC, News, Ozone, Urban Discuss now »