We have extreme sports, extreme eating contests, and extremely unbalanced political leaders on the world stage, so why not have a little extreme climate modeling for fun?
Luke Oman, a climate scientist at NASA's Goddard Space Flight Center, has long been fascinated by the potential effects of extreme events on climate. His latest adventure in extreme modeling involves looking at the climate response to the particulate matter ejected into the upper atmosphere from a regional nuclear war. Given political instability in a few known and aspiring nuclear powers, the scenario is not as far-fetched as it should be. However, the broader implications relate to potential engineered solutions to climate change from unrestrained use of carbon energy. Oman and his colleagues just presented the models at the annual meeting of the American Association for the Advancement of Science (AAAS).
The good news is that aerosols and particulates would drastically cut global warming for up to a decade.
And the bad news is that it would also drastically cut global precipitation rates for up to a decade. The declines in global temperatures and precipitation by year after the regional nuclear exchange is summarized in the following graph.
A computer model shows that global temperature change in degrees Celsius (black) and precipitation changes in millimeters per day (red) would gradually recover in the 10-year period following a the injection of 5 teragrams of black carbon particles into Earth's atmosphere.
Credit: Luke Oman and colleagues/Rutgers University
Here is Oman's description of the scenario and outcomes:
We studied the scenario of using 100 Hiroshima-size bombs, the fires from which would inject upward of 5 teragrams (megatons) of black carbon particles into Earth's upper troposphere. Observations of forest fires have shown this to occur on much smaller scales.
On the ground, global temperatures would fall by a little over 1 °C (1.8 °F) over the first three years. In contrast, aerosols from the 1991 eruption of Mount Pinatubo contributed to about 0.3 °C (~ 0.5 °F) of cooling over one year. Black carbon particles are smaller than sulfate particles and can be lofted much higher by solar heating, where their influence on climate can last up to a decade.
We also saw that two to four years after the event, rainfall would decrease globally by an average of about 10 percent.
Impacts on agriculture are likely to be severe.
"Our results suggest that agriculture could be severely impacted, especially in areas that are susceptible to late-spring and early-fall frosts," said Oman, who compared the likely post-war crop failures and famines to those that followed the 1815 volcanic eruption of Mount Tambora in Indonesia.
The results illustrate the potential and concerns associated with geoengineering schemes to address climate change from greenhouse gas emissions. Black carbon aerosols fall in the category of "solar radiation manangement" methods. Stratospheric aerosols have been examined extensively, particularly sulfates that mimic aerosols ejected from volcanic eruptions. The impacts are similar to the black carbon aerosols being modeled by Oman, namely declines in both temperature and precipitation. Drought and famine are high prices to pay to buy time to transition to a low carbon energy economy.
Impacts also need to be assessed in much more detail. For example, Trenberth & Dai (2007) have examined the observed effect of the Mt Pinatubo eruption on the hydrological cycle. They found that following the eruption there was a substantial decrease in precipitation over land with corresponding record reductions in runoff and river discharge. Using a quite detailed ocean-atmosphere GCM, Robock et al. (2008) found that injections of SO2 to enhance stratospheric aerosol would modify the Asian and African summer monsoons, reducing precipitation and thus (like climate change) potentially impacting the food supply to billions of people. Both studies suggest that major regional effects could result from sulphate geoengineering, which could counteract or reinforce those associated with climate change itself.
From Geoengineering the Climate, page 29
The utility of Oman's work is mainly in the area of strategic planning to anticipate the consequences of up to a 100 small warheads or a few larger ones in a regional conflict that escalates to a nuclear exchange. Carnage and long-term radiation contamination complete the charming scenario for strategic planners.
Some might argue that a NASA scientist modeling climate effects of a regional nuclear war is a waste of money. However, the costs are trivial unlike the massive entitlement program for fossil fuels protected by Republicans and a few Democrats. These subsidies include over $70 billion for tax breaks and incentives, most of which go to oil production. There is also the $53 billion loophole in federal royalty collection from oil wells in the Gulf of Mexico. Couple these corporate welfare programs for the most profitable corporations in human history with draconian cuts for clean, renewable energy and government services, and you have legislative stupidity almost as short-sighted as regional nuclear war.