One of the challenges in understanding climate change is that both the expected change in temperature and the effect it will have vary depending on location. So the climate in Oregon will not change in the same way as in Georgia. And even if it were, the impact of those changes will be different as the two states start off with different climates and economies. So it was a real challenge to understand the regional impact of climate change.
But the challenge is worth taking on, as most of the planning for dealing with climate change will have to take place at the regional level (particularly in the US). Now a group of researchers has built a model that tracks many of the economic impacts of climate change, and it does so for every county in the contiguous 48 states of the US. The results show that the overall impact on the country as a whole will occur by the end of this century. But the model also shows that the problems will not be evenly distributed and that the poorest provinces are likely to bear the brunt of the damage.
To generate the future temperatures, the researchers worked with the IPCC’s emission scenarios. They then used a series of simplified climate models to come up with temperature and precipitation estimates for each month at the end of this century. Each day in that month had added some weather variability to make 10 different possible scenarios. These provide the raw material for estimating economic impacts, along with a range of possible outcomes.
Specific issues, such as hurricane damage, were addressed by a combination of wind speed and storm surge models, both fed with data from historical storm tracks. The outcome of these models was then analyzed against an extensive list of coastal properties; damage was estimated using engineering models. This will give you a good idea of the complexity and level of detail of the analysis.
Here the authors turned to a series of empirical measurements of how different things change with temperature, ranging from agricultural yields to crime levels. The reliance on empirical studies is probably the study’s greatest strength, but it is also a limitation. If no one has found an empirical relationship between an economic activity and the temperature, that activity is not included. So while the study included deaths from temperature extremes, it didn’t track the health care costs of non-fatal problems — given health care costs, those are likely significant. Changes in worker productivity and changes in biodiversity were also not taken into account.
The authors also acknowledge that their analysis assumes that the population will largely remain in place. In reality, if a province becomes unbearably hot or regularly floods, there is a good chance that a large portion of the population will move, lessening the impact of these events. (Moving has its own costs, of course.)
Brace yourself for shocks
The pattern of changes is largely what you would expect: some beneficial effects are coming to the northern US, but they are largely offset by problems elsewhere. The exception to this is coastal damage, which is highly concentrated along the relatively low-lying Gulf and eastern seaboards.
So while there are fewer deaths in the northern half of the US due to extreme cold, that benefit is more than offset by sharply increased mortality in every state east of Texas and south of Kentucky. Energy costs, driven by the need for air conditioning, reflect the issues with mortality. Likewise, the fertilizing effect of CO2 will help agriculture in places like Montana and the Dakotas, but most states along the Mississippi River will be slammed.
Strangely enough, studies show that people don’t like to commit property crimes when it’s cold, while hot weather does affect property crimes. So expect an overall increase there. Violent crime, on the other hand, simply goes with the heat. As a result, the economic costs of crime will rise almost everywhere.
In general, the first bit of warming has a relatively small impact; the first 1 degree Celsius of warming only reduces national GDP by 0.6 percent. But as temperatures continue to rise, the impact becomes more severe, with the difference between 5 degrees Celsius and 6 degrees Celsius being 1.7 percent of US GDP. Not great, but not terrible.
The problem is that the consequences are worst in the provinces that are the poorest. The northeast and west coasts, the richest parts of the US, have relatively few problems in this analysis. Hardest hit are the states along the Gulf of Mexico. As a result, the authors conclude, “warming is causing a net transfer of value from the southern, central, and mid-Atlantic regions to the Pacific Northwest, the Great Lakes region, and New England.”
And the poor provinces are hit hard. The best-case scenario for a county in the poorest third of the US is a two percent loss of GDP. In the worst-case scenario, provinces will lose more than 20 percent of their GDP by the end of the century. In contrast, some northern regions will benefit net from climate change.
This paper is clearly not the last word on this analysis – in fact, the authors invite other researchers to provide additional empirical measurements of climate effects so that they can be plugged into this model. But the authors note that their estimates are in line with those for the country as a whole. And the core message is unlikely to change: as in the rest of the world, climate change is likely to exacerbate wealth disparities, which are already considered problematic.
Science2017. DOI: 10.1126/science.aal4369 (About DOIs).