What would constitute AGW being a major problem?

Ron Clutz has an excellent post. This time on he reports on A Critical Framework for Climate Change. In the post Ron looks at the Karoly/Tamblyn–Happer Dialogue on Global Warming at Best Schools particularly at Happer’s major statement. In my opinion these dialogues are extremely useful, as (to use an old-fashioned British term) are antagonists are forces by skilled opponents to look at the issues in terms of a level playing field. With the back and forth of the dialogue, the relative strengths and weaknesses are exposed. This enables those on the outside to compare and contrast for themselves. Further, as such dialogues never fully resolve anything completely, can point to new paths to develop understanding. 

Ron reprints two flow charts. Whilst the idea is of showing the issues in this way to highlight the issues is extremely useful correct. I have issues with the detail. 


In particular on the scientific question “Is it a major problem?“, I do not think the “No” answers are correct.
If there was no MWP, Roman warming, or Bronze Age warming then this would be circumstantial evidence for current warming being human-caused. If there has been 3 past warming phases at about  1000, 2000 and 3000 years ago, then this is strong circumstantial evidence that current warming is at least in part due to some unknown natural or random factors. Without any past warming phases at all then it would point to the distinctive uniqueness of the current warming, but that still does not mean not necessarily mean that it is a major net problem. There could be benefits as well as adverse consequences to warming. But the existence of previous warming phases under many studies and only being able to claim by flawed statistics that the majority of warming since 1950 in human-caused (when there was some net warming for at least 100 years before that suggests a demonstrable marginal impact of human causes far less than 100% of total warming. Further there is issues with

(a) the quantity of emissions a trace gas to raise that the atmospheric levels by a unit amount

(b) the amount of warming from a doubling of the trace gas – climate sensitivity

(c) the time taken for rises on a trace gas to raise temperatures.

As these are all extremely difficult to measure, so a huge range of equally valid answers. It is an example of the underdetermination of scientific theory.

At the heart of the underdetermination of scientific theory by evidence is the simple idea that the evidence available to us at a given time may be insufficient to determine what beliefs we should hold in response to it.

But even if significant human-caused warming can be established, this does not constitute a major problem. Take sea-level rise. If it could be established that human-caused warming was leading to sea level rise, this may not, on a human scale, be a major problem. At current rates sea levels from the satellites are rising on average by 3.5mm per year. The average adjusted level from the tide gauges are less than that – and the individual tide gauges show little or no acceleration in the last century. But if that rate accelerated to three or four times that level, it is not catastrophic in terms of human planning timescales. 

The real costs to humans are expressed in values. The really large costs of climate change are based not so much on the physical side, but implausible assumptions about the lack of human responses to ongoing changes to the environment. In economics, the neoclassical assumptions of utility maximisation and profit maximisation are replaced by the dumb actor assumption.

An extreme example I found last year. In Britain it was projected that unmitigated global warming could lead to 7000 excess heatwave deaths in the 2050s compared to today. The projection was most of these deaths would occur in over 75s dying in hospitals and care homes. The assumption was that medical professionals and care workers would carry on treating those in the care in the same way as currently, oblivious to increasing suffering and death rates.  

Another extreme example from last year was an article in Nature Plants (a biology journal) Decreases in global beer supply due to extreme drought and heatThere were at least two examples of the dumb actor assumption. First was failure by farmers to adjust output according to changing yields and hence profits. For instance in Southern Canada (Calgary / Edmonton) barley yields under the most extreme warming scenario were projected to fall by around 10-20% by the end of the century. But in parts of Montana and North Dakota – just a few hundred miles south – they would almost double. It was assumed that farmers would continue producing at the same rates regardless, with Canadian farmers making losses and those in Northern USA making massive windfall profits. The second was in retail. For instance the price of a 500ml bottle of beer in Ireland was projected to increase under the most extreme scenario in Ireland by $4.84 compared to $1.90 in neighbouring Britain. Given that most of the beer sold comes from the same breweries; current retail prices in UK and Ireland are comparable (In Ireland higher taxes mean prices up to 15% higher); cost of a 500ml bottle is about $2.00-$2.50 in the UK; and lack of significant trade barriers, there is plenty of scope with even a $1.00 differential for an entrepreneur to purchase a lorry load of beer in the UK and ship it over the Irish Sea. 

On the other hand nearly of the short-term forecasts of an emerging major problem have turned out to be false, or highly extreme. Examples are

  • Himalayan Glaciers will disappear by 2035
  • Up to 50% reductions in crop yields in some African Countries by 2020
  • Arctic essentially ice-free in the summer of 2013
  • Children in the UK not knowing what snow is a few years after 2000
  • In the UK after 2009, global warming will result in milder and wetter summers

Another example of the distinction between a mere difference and a major problem is the February weather. Last week the UK experienced some record high daytime maximum temperatures of 15-20C. It was not a problem. In fact, accompanied by very little wind and clear skies it was extremely pleasant for most people. Typical weather for the month is light rain, clouds and occasional gales. Children on half-term holidays were able to play outside, and when back in school last week many lessons were diverted to the outdoors. Over in Los Angeles, average highs were 61F (16C) compared to  February average of 68F (20C). This has created issues for the elderly staying warm, but created better skiing conditions in the mountains. More different than a major problem. 

So in summary, for AGW to be a major problem it is far from sufficient to establish that most of the global warming is human caused. It is necessary to establish that the impact of that warming is net harmful on a global scale.

Kevin Marshall