An analysis by atmospheric scientists at Stanford University in Palo Alto, California, has shown that, in the Arctic, aircraft vapour trails have caused 15–20% of surface warming.

Globally, commercial aircraft vapour trails have been responsible for 4–8% of surface warming since records began in 1850 - equivalent to a temperature increase of 0.03–0.06°C.

Previously, it had been assumed that the impact of aircraft emissions was the same everywhere. The new analysis, led by Mark Jacobson, a professor of civil and environmental engineering at Stanford, reveals that aircraft emissions increase the fraction of cirrus clouds where vapour trails are most abundant but, in other locations, the main effect is to decrease temperatures in the lower atmosphere, thereby reducing relative humidy and reducing the fraction of cirrus clouds.

Black carbon emission from aircraft also play an important role in determining whether cirrus cloud formation occurs. The researchers concluded that, If black-carbon emissions from aircraft could be reduced 20-fold, the warming resulting from vapour trails would be halted and a slight cooling would occur.

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According to scientists at Luleå University of Technology in Sweden, attempting to tackle global warming by capturing carbon dioxide or switching to nuclear power will not work because a large part of the warming results from the heat produced by industrial processes rather than the greenhouse effect.

In a paper published in the International Journal of Global Warming, Bo Nordell and Bruno Gervet  have calculated the total energy emissions from the start of large-scale industrialisation in the 1880s to the modern day  They point out that net heat emissions during that time account for almost three quarters of the global warming during that period - the greenhouse effect accounts for the remaining 26%.

The implication of their findings are  that those processes which produce heat, such as burning fossil fuels and using nuclear power, would continue to cause global warming even if all of the carbon dioxide which they emit is captured. On the other hand, those sources of energy which ultimately use the sun’s heat, including wind and marine power as well as solar, do not contribute to global warming.

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British researchers, writing in the Current Biology journal, say that growing crop varieties that reflect more sunlight into space could cool much of Europe, North America and parts of North Asia by up to one degree Celsius during the summer growing season.

"We found that different varieties of most food crops do differ in how much solar energy is reflected back to space,"  said Andy who led the study. "The more energy you reflect back to space the cooler the air temperatures will be."

Previous research has shown that wheat, maize, barley and sorghum reflect solar energy differently, depending on either how waxy a plant’s surface is, how the leaves are arranged or how hairy they are. The same probably holds true of all food crops,

"The idea is you could continue to grow maize, for example, but you could grow a variety that has a bigger climate benefit," Ridgwell said. "You could use selective breeding for climate characteristics. This seems very doable without spending lots of money."

The effect would occur mainly in Europe, North America and Northern Asia where most of the world’s croplands are located.

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Australia’s "60 Minutes" has broadcast an item called "Crunch Time" which made much of the opinions of David Evans, a computer programmer with a PhD in electrical engineering who once worked on a mathematical modeling program for the Australian Greenhouse Office. Dr Evans put two arguments to support his view that global warming is not caused by carbon emissions. Dr Evans first point was that, although carbon emissions have continued to increase, global temperatures have not increased for the last eight years. Here is the graph of global temperatures from  the UK Met. Office’s Hadley Centre. It’s difficult to see Dr Evan’s evidence that temperatures have stopped going up.

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Many climate change campaigns have used the dramatic photographs of the diminishing snow of Kilamanjara as evidence of global warming.

In fact, the snows have been retreating for decades - perhaps centuries. The real reason for the diminishing snows is deforestation at the base of the mountain. This has resulted in less moisture in the air around the mountain and, consequently, in less snow falling on the peak.

Of course, the fact that diminishing snows on Kilamanjaro is not the result of global warming is no evidence that global warming is not real.

Photos taken on Feb 17 1993 and Feb 21 2000 (Public domain)

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Climate Change Slideshows seem to fashionable. Here’s mine (developed in conjunction with GoBizGreen):

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