This certainly won’t change many skeptics’ minds… but for everyone else it further emphasizes the dangers (as if more were needed).
What mainly motivates the skeptics, it seems, is fears about the costs of reducing emissions of greenhouse gases, especially CO2. That will certainly entail costs, but even those are not easy to predict. Ironically, and unfortunately for the companies involved, the cost of photovoltaic energy has been plummeting, as the required materials (especially polysilicon) have become much cheaper. This, along with limitations on demand due to economic turbulence (especially in Europe), has put a number of solar companies out of business. But the trend is clear: photovoltaic energy, and other forms of solar energy, just keep getting more affordable. The exact opposite is true for fossil fuels, even without taking account of global warming and other externalities.
It’s not so hard to predict that there will be significant effects of accelerated global warming, but it’s harder to predict the timing and magnitude of the effects and their costs. Some costly effects seem pretty likely, such as extended periods of drought in many places, loss of habitable land, due to sea level rise, where many millions of people now live, poorer health and more deaths due to higher temperatures and severe shortages of food and potable water. And so forth.
And then there are the wildcards associated with extreme weather – severe flooding, more frequent and more intense hurricanes and tornadoes, forest fires resulting from prolonged heat waves.
Some of these extremes appear to be nearly certain, while others remain unpredictable possibilities. But even the possibilities, and their costs, need to be accounted for in terms of increased statistical expectation. You don’t know how much you’ll lose during a weekend at the Las Vegas casinos, but if you look at the odds (and the profits the casinos make), you can calculate the expected loss.
Extreme weather, such as the 2010 Russian heat wave or the drought in the horn of Africa, will become more frequent and severe as the planet warms, the Intergovernmental Panel on Climate Change (IPCC) warns in a report released today. Some areas could become “increasingly marginal as places to live in”, the report concludes.
It is “virtually certain” — meaning 99–100% probability in IPCC terminology — that the twenty-first century will see an increase in the frequency and magnitude of warm temperature extremes and a decrease in cold extremes.
It is much less clear, however, how climate change will affect rainfall, flood risk and storminess.
And these weather events aren’t independent things either. Extremes in one part of the global weather system can lead to extremes in other parts. For example, the 2010 Russian heat wave and the severe flooding in Pakistan. (References: here, here)
It’s unfortunate that people don’t have too much trouble understanding the need to prepare for unpredictable events like earthquakes or even asteroid impacts – yet there’s so much reluctance to do anything about far more predictable outcomes associated with extreme weather.