Global Cooling
There has been a lot of debate about global warming this past year as temperatures have failed to rise. Of course climate is a complex topic and there are many factors that contribute to how warm or coool a particular year will be. Everything from sunspots to ocean currents have an important impact on global temperatures. In the long term, however, scientists claim that we humans are placing strong positive pressure on temperature through emissions of green house gases. This may be, but as far as I remember there are actually two types of ‘manmade’ emissions that effect climate. They are:
1) Greenhouses gases - Contribute to higher temperatures and can last in the air for hundreds of years
2) Particulate emissions - Emissions that reflect sunlight and reduce temperature. Generally emitted by dirty fuel sources such as coal.
Given that there are these two key manmande emissions the important factors on there impact are.
The key insight I have gleamed from a lifetime of reading the news is that particles last in the atmosphere for only up to ~30 years, while greenhouse gases will remain much longer (depends on how fast they are scrubbed by forests, etc). If we were to assume that both gases were output at the same rate and had the same impact on temperatures, than for the first 30 years manmade gases would have no impact on temperatures, but thereafter greenhouses gases would have a great impact than reflective particles, and temperatures would rise.
But all things are not equal. Two key insights appear to be
1) In general, more advanced economies have cleaner emissions that output a higher ratio of greenhouse gases to particulate matter (though lower amounts of both, per unit energy).
2) Given a constant proportion of greenhouse gases to particulate emissions, the net impact of emissions will be to have a negative impact on temperatures in the short run, and a positive impact on the long run.
Insight 1 implies that the higher the proportion of emissions from the developing nations the relatively higher amount of reflective particles in the air to greenhouses gases. Insight 2 Implies that the faster the rate that emissions increase the cooler the earth gets. The slower the rate, the warmer the earth gets.
The key implication is that, given the rapid rise of China and its massive and dirty emissions, global warming from human emissions should slow dramatically. It also implies that the more rapidly we switch to clean energy sources, the higher temperatures will be in the short and medium term.