Letter to Christchurch Press from David Beach, 4 Aug 2015. Click to enlarge.
David Beach sent a letter to the Christchurch Press published 4 August, 2015, which contains grievous errors. Whatever he intends by the use of the term ‘exponential’, we can only take it in its usual sense of increasing at a more and more rapid rate, or a rate expressed by a mathematical exponent. His salient point is this:
First, the 1m figure is absolutely the best case for sea level rise. The worst case (expressed by an expert team led by Dr Hansen) is 5m. Second, it does not stop at whatever figure turns out to be true, as it increases exponentially.
This is very wrong. It contradicts not only the latest report, AR5 (2013), from the IPCC, the world’s foremost climate authority, but also the extensive local knowledge and expertise of New Zealand marine scientist Professor Willem de Lange.
Five years ago, Professor de Lange sent me this graph showing the probabilities of various marine events occurring in New Zealand by 2100.
Probabilities of various marine events in NZ before 2100.
There’s little chance that in only five years since then these probabilities have altered to any meaningful degree. Prof de Lange is among the foremost ocean scientists in New Zealand. Solid evidence is required to contradict his opinion. I’ll look up the IPCC projections for sea level rise in AR5, but I seem to recall it sits at about 450mm by 2100—less than half of Beach’s “best case”.
Notwithstanding the firm belief David Beach holds in the matter of sea level rise in the distant future, in the absence of evidence it’s hard to think that he could be more wrong.
UPDATE 6 Aug 2015 1225 NZST
We need to know more about the IPCC’s calculation of sea level rise, but however they deal with it, it must begin with our emissions increasing the heat energy in the climate system. So before I leave this post let me raise for your consideration this interesting description from AR5 of gaseous temperature influences. It seems to see differences between the radiative forcings from GHG and water vapour, but it is unpersuasive. Temperature has no “structure” I’ve heard of; if water vapour is the strongest GHG by far, why is it not a significant initial forcing? What’s the difference between a “significant initial forcing” and a “fundamental agent” of climate change? The GHG don’t change climate, but temperature. Richard Cumming is adamant that CO2 has no effect on the TOA energy balance yet could CO2 still be necessary to protect atmospheric water vapour? Perhaps someone will untangle this.
Currently, water vapour has the largest greenhouse effect in the Earth’s atmosphere. However, other greenhouse gases, primarily CO2, are necessary to sustain the presence of water vapour in the atmosphere. Indeed, if these other gases were removed from the atmosphere, its temperature would drop sufficiently to induce a decrease of water vapour, leading to a runaway drop of the greenhouse effect that would plunge the Earth into a frozen state. So greenhouse gases other than water vapour provide the temperature structure that sustains current levels of atmospheric water vapour. Therefore, although CO2 is the main anthropogenic control knob on climate, water vapour is a strong and fast feedback that amplifies any initial forcing by a typical factor between two and three. Water vapour is not a significant initial forcing, but is nevertheless a fundamental agent of climate change.
– AR5, Chp 8 Anthropogenic and Natural Radiative Forcing, p.667