DARA International, representing 20 nations, has released a new report on climate change estimating 6 million annual deaths and 3.2% of GDP lost from climate change by 2030. The news is lighting up with reports about this study, some critiquing it as alarmist, some welcoming it as speaking truth. Granted, these numbers seem pretty outrageous, but the numbers are not the most important part of this report. What'€™s most important is the general relationship of impacts to each other, the approximate magnitude of those impacts, and what those two things mean for global health.
Let's talk a bit about models like the one used to create this report. Models don'€™t predict the future, and they don'€™t purport to. What they do show us is a potential, even likely, future given the set of assumptions the model uses. Model operators are looking to put in the assumptions that best describe the system (the earth, the economy, etc), in order to get the most informative results. What is important and useful is when multiple groups independently develop and run models trying to capture the same phenomena. Where the results of all (or most) models agree is where you can have the most certainty in the impact or change being described.
Methodology certainly still matters, and the report comes with a 100 page document detailing their methods. I have not been through all of it yet, but everything I have seen so far indicates the authors knew what they were doing. This study in particular was a fingerprint study—€“ a study that attempts to assign causal factors to incidents already in progress by determining deviation from a baseline and accounting for other variables. These are incredibly helpful in parsing out where climate change is already happening and validating past predictions.