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Two Kinds of Abrupt Climate Change Likely Before 2100

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A 2013 federal report catalogs multiple stressors that are pushing natural and human systems towards their limits. In this context, climate change creates the potential for abrupt large-scale changes in climate or other natural systems. The report seeks to assess the likelihood of whether such abrupt change is likely in this century, or whether change is expected to be more gradual, occurring primarily after 2100.

The report finds that many of the processes it reviews are individually likely to cause substantial environmental changes, but only two are likely to do so abruptly in this century. The report also finds that it is not really possible at this time to predict what the changes will be. And it also finds that it is not really possible to know how the processes will interact with each other. Consequently, the report’s subtitle is “Anticipating Surprises.”

For the purposes of the report, a change is considered abrupt if it would occur at a rate that would challenge the adaptive capacity of the system it affected. For instance, even though it might take decades, if sea level rose faster than we could relocate the buildings and infrastructure that would be flooded, then it would be considered abrupt. Alternatively, previous episodes when the earth’s climate has changed (the onset and the ends of ice ages), species appear to have been able to shift their range at a rate up to 1.0 km. per year. The report would not consider that abrupt. But at the current rate of climate change, they may have to shift their range more than 4 km. per year. If that exceeds their capacity, then it would be considered abrupt.

The report examines 14 specific processes that could lead to abrupt change that could meaningfully alter the climate of the earth and its ability to support the rich and abundant life it now sustains. Here is a summary:

Extinction of large numbers of species (both ocean and land): HIGH chance of an abrupt change in this century; VERY HIGH chance for a significant change after 2100.

Disappearance of Arctic Sea ice in late summer: HIGH chance of an abrupt change in this century; VERY HIGH chance for a significant change after 2100.

Disappearance of Arctic sea ice during winter: LOW chance of an abrupt change in this century; MODERATE chance for a significant change after 2100.

Disruption to the Atlantic Meridional Overturning Circulation: LOW chance of an abrupt change in this century; HIGH chance for a significant change after 2100.

Sea level rise due to ocean thermal expansion: LOW chance of an abrupt change in this century; HIGH chance for a significant change after 2100.

Sea level rise due to destabilization of West Antarctic Ice Sheet: unknown (but probably LOW) chance of an abrupt change in this century; UNKNOWN chance of significant change after 2100.

Sea level rise due to the melting of other ice sheets, including Greenland; LOW chance of an abrupt change in this century; HIGH chance of significant change after 2100.

Decrease of oxygen levels in the oceans (threats to marine life): MODERATE chance of an abrupt change in this century; HIGH chance of significant change after 2100.

Changes to major climate patterns (e.g. El Niño, annular modes): LOW chance of an abrupt change in this century; MODERATE chance of significant change after 2100.

Increase in intensity, frequency, and duration of heat waves: MODERATE chance of an abrupt change in this century; HIGH chance of significant change after 2100. Pattern expected to be regionally variable.

Increase in frequency and intensity of extreme precipitation events ( droughts/floods/hurricanes/major storms): MODERATE chance of an abrupt change in this century; MODERATE-to-HIGH chance of significant change after 2100.

Release of carbon stored in soils and permafrost: LOW chance of an abrupt change in this century; HIGH chance of significant change after 2100.

Release of methane from ocean methane hydrates: LOW chance of an abrupt change in this century; MODERATE chance of significant change after 2100.

Collapse or other rapid change to whole ecosystems: MODERATE chance of an abrupt change in this century; HIGH chance of significant change after 2100.

This report is written at a global level. It contains no information that is specific to Missouri. I don’t know of any document that contains such information. For my next post, I’ll try to make a few speculations based on the information from the various reports I’ve reviewed in posts up to now.

Source:

Committee on Understanding and Monitoring Abrupt Climate Change and Its Impacts. 2013. Washington, DC.: National Academies Press. http://www.nap.edu/catalog.php?record_id=10136.

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