Climate Letter #1082

New light is shed on the consequences of removing aerosols that now reflect sunlight.  A new study tends to confirm common estimates that the sulfate aerosols emitted by burning fossil fuels have a cooling effect equal to at least 0.5C, or up to 1.1C, globally averaged, which will quickly decline if and when we reduce burning the fuels.  The Northern Hemisphere is especially sensitive.  (This is an unavoidable complication that will have to be reckoned with, possibly resolved by injecting sulfates back into the atmosphere by other means, which has its own set of potential problems.)
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Climate change is having a serious impact on Iran (Scientific American).  Severe drought and dust storms, which have become more common in the region, have had a ravaging effect on family farms.  Current government policies have aggravated the problem for the poorest classes. Also, Iran’s temperatures, like those throughout the Persian Gulf, are among the highest in the world and are increasing toward levels that are unbearable when heatwaves occur.
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Effects of climate change are causing outmigration from Vietnam’s Mekong Delta.  One of Earth’s most productive agricultural regions, with 18 million inhabitants, has proven vulnerable to a set of changes that frequently result in salt water intrusions that destroy crops.  Periodic drought and flooding events have added to frustrations.
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New revelations about what causes methane to be released from hydrate formations.  Under current conditions the best evidence points to pressure relief rather than warmer temperatures.  Pressure is reduced today in a few spots where the local seafloor is rising for some reason, reducing the weight of the water above.  The coming sea level rise will thus generally favor containment, even if bottom waters grow warmer, which should allay fears of runaway emissions from this source at any time soon.
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How El Nino and La Nina affect Antarctic ice shelves.  It’s mass that counts, not thickness, and the opposing effects are quite interesting.  Expectations favor greater frequency of extreme El Nino events in the future, suggesting a quickening of the rate of sea level rise.
Carl
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