A long time ago, in About this Blog I wrote:
Opinions are often interesting and sometimes entertaining. But what do we learn from opinions? It’s more useful to understand the science behind the subject. What is this particular theory built on? How long has the theory been “established”? What lines of evidence support this theory? What evidence would falsify this theory? What do opposing theories say?
Now I would like to look at impacts of climate change. And so opinions and value judgements are inevitable.
In physics we can say something like “95% of radiation at 667 cm-1 is absorbed within 1m at the surface because of the absorption properties of CO2″ and be judged true or false. It’s a number. It’s an equation. And therefore the result is falsifiable – the essence of science. Perhaps in some cases all the data is not in, or the formula is not yet clear, but this can be noted and accepted. There is evidence in favor or against, or a mix of evidence.
As we build equations into complex climate models, judgements become unavoidable. For example, “convection is modeled as a sub-grid parameterization therefore..”. Where the conclusion following “therefore” is the judgement. We could call it an opinion. We could call it an expert opinion. We could call it science if the result is falsifiable. But it starts to get a bit more “blurry” – at some point we move from a region of settled science to a region of less-settled science.
And once we consider the impacts in 2100 it seems that certainty and falsifiability must be abandoned. “Blurry” is the best case.
Less than a year ago listening to America and the New Global Economy by Timothy Taylor (via audible.com) I remember he said something like “the economic cost of climate change was all lumped into a fat tail – if the temperature change was on the higher side”. Sorry for my inaccurate memory (and the downside of audible.com vs a real book). Well it sparked my interest in another part of the climate journey.
I’ve been reading IPCC Working Group II (wgII) – some of the “TAR” (= third assessment report) from 2001 for background and AR5, the latest IPCC report from 2014. Some of the impacts also show up in Working Group I which is about the physical climate science, and the IPCC Special Report on Managing the Risks of Extreme Events and Disasters to Advance Climate Change Adaptation from 2012, known as SREX (Special Report on Extremes). These are all available at the IPCC website.
The first chapter of the TAR, Working Group II says:
The world community faces many risks from climate change. Clearly it is important to understand the nature of those risks, where natural and human systems are likely to be most vulnerable, and what may be achieved by adaptive responses. To understand better the potential impacts and associated dangers of global climate change, Working Group II of the Intergovernmental Panel on Climate Change (IPCC) offers this Third Assessment Report (TAR) on the state of knowledge concerning the sensitivity, adaptability, and vulnerability of physical, ecological, and social systems to climate change.
A couple of common complaints in the blogosphere that I’ve noticed are:
- “all the impacts are supposed to be negative but there are a lot of positives from warming”
- “CO2 will increase plant growth so we’ll be better off”
Within the field of papers and IPCC reports it’s clear that CO2 increasing plant growth is not ignored. Likewise, there are expected to be winners and losers (often, but definitely not exclusively, geographically distributed), even though the IPCC summarizes the expected overall effect as negative.
Of course, there is a highly entertaining field of “recycled press releases about the imminent catastrophe of climate change” which I’m sure ignores any positives or tradeoffs. Even in what could charitably be called “respected media outlets” there seem to be few correspondents with basic scientific literacy. Not even the ability to add up the numbers on an electricity bill or distinguish between the press release of a company planning to get wonderful results in 2025 vs today’s reality.
Anyway, entertaining as it is to shoot fish in a barrel, we will try to stay away from discussing newsotainment and stay with the scientific literature and IPCC assessments. Inevitably, we’ll stray a little.
I haven’t tried to do a comprehensive summary of the issues believed to impact humanity, but here are some:
- sea level rise
- more powerful cyclones and storms
- food production
- ocean acidification
- extinction of animal and plant species
- more pests (added, thanks Tom, corrected thanks DeWitt)
- disease (added, thanks Tom)
Possibly I’ve missed some.
Covering the subject is not easy but it’s an interesting field.