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I wonder how coral reef bleaching (the destruction of the great barrier reef over the past 2 years) and the migration of infectious agents further north with climate change will factor in.
Yes. It's a bit Deja vu, though, for those remembering the forest dieback scare around 1980. It was a huge environmental issue in eastern Europe, Scandinavia, north-west Russia and to some degree in north America, I believe. It was a fact in those days that the forests were dying mass scale, that more than 50% of the trees in several countries were affected, and the consensus was that the cause was soil acidification due to industrial SO2
pollution. Researchers did large surveys and found evidence of affected trees at a large scale even far from the industrial areas responsible for the pollution, even worse the further away the trees were, calling for immediate inter-governmental action. Scientists were dead seriously predicting that much of the forest would simply be gone by 2000. So what happened?
pollution was real and caused some real, though not catastrophic problems (acidification of lakes, for instance). But the forest dieback was greatly exaggerated and the soil acidification hypothesis was simply not correct. When forests in Scandinavia were surveyed, it was to assess the SO2
damage, and the finds were accordingly misinterpreted. In reality most of the damage was natural, caused by fungi or salt or other causes. For instance, when it was found that coastal areas were worst hit, it fitted nicely with the idea of airborne pollution from industrial Europe, since most precipitation falls near the coast. In reality the researches were mostly seeing the effect of salt in the air. There were scientists pointing out the possibilities of natural causes and that the damage might not be entirely new, but such talk was highly unpopular. The causes were complex, but you can't present something ambiguous publicly.
The catastrophe didn't happen. The scare did lead to actions against SO2
pollutions and emissions were reduced. Did it save the forests? That would be stretching the truth quite a bit. Then it might be argued that the exaggeration was necessary to reduce the unhealthy SO2
emissions. Perhaps, but dishonesty can backfire.
Is coral bleaching a similar exaggeration? It will be interesting to see. There's no way we can turn down the sea temperature in a few decades anyway.
A good example of this, and in my opinion one of the most worrying, is food security. Agriculture is impacted by a combination of higher evapotranspiration rates, increased drought frequency and severity, and loss of arable land in low lying river deltas due to sea level rise and salt intrusion. Some have suggested that the increased CO2 in the atmosphere would help, and in fact it does, but not nearly enough to offset these other factors.
More atmospheric CO2
helps, and there are other benefits from warming. It's pretty obvious that a warmer climate will increase the growing season at higher latitudes, where most of the warming is expected, and will push the arable limit further. The tricky bit is to determine how much warming can be had before negative consequences cancel the benefits. Currently, the situation doesn't look so bad. In my lifetime the world populations has doubled, yet there are fewer who starve (both relatively and absolutely). Of course, this has more to do with globalisation and improved technology than with warming. In other words we're much better prepared for climatic changes than previous generations were.