By Peter Sergienko

In a paper published in the Proceedings of the National Academy of Sciences on April 8, researchers have projected changes in suitable growing regions for wine grape production in 2050 using runs on 17 different global climate models and assuming two different carbon emissions scenarios. The findings project major global geographic shifts in suitability for viticulture, with significant declines in traditional wine producing regions with Mediterranean climates such as Bordeaux, Rhone and Tuscany. Current suitability is retained in smaller areas, especially at higher elevations and in coastal areas. Increases in suitability are projected in more northern regions in North American and Europe.

Because climate stability is critical to all agriculture, it is important to look briefly at the greenhouse gas emissions scenarios incorporated in the models and to consider other scientific literature addressing climate stability, climate equilibrium, and the relative importance of both mitigation of and adaptation  to climate change to put the study’s findings into context.

The two emissions scenarios considered in the study are “Representative Concentration (or Carbon) Pathways (RCP) 8.5 and 4.5. RCP 8.5 is a business as usual scenario with no coordinated global effort to cap and reduce global greenhouse gas emissions through the year 2100. More information concerning RCPs is here.

Notwithstanding all current voluntary and compulsory efforts by private businesses and individuals, states, local governments, and many countries to reduce greenhouse gas emissions, RCP 8.5 is a road to catastrophe. The effects of this scenario on wine grape production in 2050 are probably irrelevant because successful human adaptation to the changes in climate under this emissions pathway is unlikely.

RCP 4.5 is considered to be a “weak mitigation” emissions scenario. Notably, the projected global average temperature increase by 2100 under this scenario ranges from 2.25 to 4.11 degrees Celsius with a 53 percent chance of keeping the increase below 3 degrees Celsius. In general, all greenhouse gas emissions policies under consideration nationally and internationally are designed with the goal of keeping the temperature increase below 2 degrees Celsius. This goal is somewhat arbitrary and based on dated science. A safer goal is likely 1.5 degrees Celsius.
Whether or not the 2 degree Celsius goal is already beyond reach, mitigation to prevent as much warming as possible and to stabilize climate as soon as possible is critically important to wine grape growers and to all agriculture for two basic reasons.

First, as the study suggests, the lower the future greenhouse gas emissions are, the greater the chances of successful adaptation in place by changes in practices, such as water use for misting or sprinkling to reduce grape temperatures on the vine. Once adaptation in place becomes impossible, the only alternative is to move into new areas that are suitable for wine grape growing. This form of adaptation is fraught with many problems for current growers, including loss of existing land value and competition for new, suitable land.

Second, successful adaptation by moving into new areas that are suitable for viticulture (and for any crop) depends in large part on future climate stability. Recognizing that climate change is largely irreversible and, depending on emissions scenarios, climate stability may not be reached by 2100 or even 2200, let alone by 2050, is critically important to understand the priority and importance of mitigation over adaptation. If we have to move crops to new areas because of climate change, we certainly don’t want to move them every 30 or 50 years because the future climate is still unstable. A good article discussing climate stability and irreversibility with many links to source materials is here.

The most important aspect of the study is to make us look at probable future climate change and how it would impact a specific and vital agricultural industry. It is very difficult to envision the world in 2100 and beyond. Unfortunately, much of climate change discussion is taking place in that context. 2050 is within many of our lifetimes and certainly within the lifetimes of most of our children and grandchildren. If we want to preserve the opportunities for them that we have enjoyed, studies such as this make a compelling case for policies that will result in peak global greenhouse gas emissions no later than 2020 with significant annual emissions reductions to near zero by mid-century following the peak.

More coverage of the paper can be found in this article in The Guardian.