Climate change debate
13/08/2012 § 3 Comments
Last week, I was reading a report on the economic impacts of climate change on New Zealand’s agricultural sector. I have written one or two such reports myself and try to keep up with other people’s research. It struck me that there’s a huge difference between these academic or policy documents and the public debate in the popular media.
The academic and policy documents make it very clear that climate change is neither good nor bad for New Zealand. The main variables are temperature, rainfall, and distribution of extreme events. That last variable is difficult to analyse, so it generally comes down to the first two. The impacts are quite different by region. In some areas, a little more warmth and rain make everything grow better. In other areas, reduced rainfall makes farming more difficult.
Climate change researchers try to grapple with this variation with a series of models built on models. The main IPCC climate change scenarios are analysed with global climate models. The modellers feed in a set of assumptions and see what happens to different regions, but these regions are defined fairly broadly. Then, those modellers feed in a new set of assumptions to see what happens.
New Zealand researchers then have to take the international results and downscale them to account for local variations. That’s another set of modelling. The downscale modelling has to choose which internal climate change model and which scenario from that model to use as a basis. For example, a lot of New Zealand work relies on the HadCM3 (Hadley Centre Coupled Model v3) international model, and tends to start with the ‘central’ scenarios as opposed to the extreme ones.
There is also the very important question of how people will adapt. New Zealand is generally temperate and well supplied with water. Other countries are very successful with higher temperatures and less rainfall, so it’s clear that we could make a few changes and still live fairly well.
The economic research is essentially a large number of chained assumptions from scenario to international model to downscaling model to economic model. At each step along the way, we could have informed and thoughtful debates: how we select likely scenarios, which international model is best for New Zealand, how downscaling captures local conditions, how weather affects production, the extent and speed of economic adaptation, etc.
Instead, the popular media seems stuck in a loop. Is climate change happening? Are humans to blame? When will we run out of time?
It’s climate change as soap opera. Which suggests we’ll be seeing the same storylines in another 50 years, just with a new cast of characters.