Stephan Harrison responds to Ian Plimer's climate change posting

A very comprehensive response to Prof. Ian Plimer’s email of 20th October has just been sent to me by Dr. Stephan Harrison of University of Exeter:

I will respond to Plimer’s main points. This will be a long posting, so apologies! I will identify Ian Plimer’s points as (IP) and my response as (SH).

(IP) It is claimed that there is a scientific consensus about human-induced climate change. There is no consensus. Consensus is a process of politics, not science. Science is married to evidence, no matter how uncomfortable.
(SH) The word consensus is used to show that the overwhelming majority of informed scientists agree that there is a greenhouse effect; that C02 is a greenhouse gas (GHG hereafter) and that these have increased enormously in the atmosphere and that recent warming is largely being driven by this. There is also consensus in other parts of science (Newtonian Physics, Quantum Physics, Evolution etc.). Are these also politically driven?
(IP) Scientists who push the view that humans create climate change are young, trying to forge a career in a narrow field by fear, seek government and research grant favour and base their opinions on computer projections about the future. There are no natural scientists I know who have spent more than 40 years of integrated inter-disciplinary science who argue that humans change climate.(SH) Nonsense. I know lots of scientists at the beginning and end of their careers who accept the science of Anthropogenic Global Warming (AGW). At both Exeter and Oxford Universities, where I recently taught, both places were full of them. Actually, the way to make a real name for yourself as a scientist would be to show that AGW wasn’t happening. If you could do that then you would become the most famous scientist in the world. It’s telling that no-one has managed this….including IP.
(IP) To argue that temperature has increased 0.80C since 1850 is misleading because the Little Ice Age ended in 1850 and it is absolutely no surprise that temperature increases after a long cold period.
(SH) Why is it no surprise? Why should temperatures increase? They only do this in response to the forcings; and since the middle of the 20th century the GHG forcings have begun to overwhelm the natural variability in the climate. IP’s mistake is to think that the climate acts like a rubber ball. Just because it was cold in one period, doesn’t mean that it has to be warm in the next!
(IP)Since 1850, there has been temperature increase (1860-1880, 1910-1940, 1976-1998) and decrease (1880-1910, 1940-1976, 1998-present) and the rate of the three periods of temperature increase has been the same.(SH). No, this is wrong. The have been no GLOBAL increases in temperature in the instrumental record comparable to the present one (since 1975 or so). And temperatures since 1998 have NOT fallen…they’ve risen. Look at the data!
(IP) A simple question does not get asked: what part of warming and cooling since 1850 is natural? The first two warmings could not be related to human additions of CO2 from industry hence why wouldn't the 1976-1998 warming also be due to natural processes?(SH) This question is regularly asked! That’s why we do attribution studies. IP needs to read the attribution literature…if he thinks it’s wrong then he could try to develop an attribution that explains the present warming and temperature changes over the past 100 years without, aerosol, volcanic and GHG forcing.
(IP) It is claimed that, since 1950, human additions of CO2 has been the dominant cause of warming. What is not mentioned is that CO2 is plant food, not a pollutant, and without CO2 there would be no life on Earth.
(SH). Irrelevant. Lots of things are pollutants at high levels and not at low levels. Try drinking 10 litres of water quickly and you’ll see what I mean (it will kill you).
(IP)The scales and rates of temperature change in the past have been far greater than when humans emitted CO2 from industry. What has caused the cooling (1940-1976 and 1998-present) or, by some tortured logic, is global cooling in this century actually global warming cunningly disguised? (SH) The cooling in the mid-century (which was very mild and nowhere near as marked as shown in IP’s manufactured temperature graph) is attributed to a combination of aerosol and natural variability. There has been no cooling since 1998.
(IP)At present, atmospheric temperature is decreasing and CO2 is increasing, again showing that CO2 is not the principal driver of climate change.
(SH). Irrelevant and shows misunderstanding. Firstly T is NOT decreasing. Second, there is natural variability. In a dynamic climate system over short periods (less than 15 years or so) the T signal is as large as the noise. That means the natural variability can mask the T signal. A couple of years ago we had a warm spell in April and a cold spell in May. No doubt IP would use these data to argue that summer wasn’t coming and that the seasons aren’t driven by insolation!
(IP)Planet Earth is a warm wet greenhouse volcanic planet. The planet is dynamic; change is normal. Five of the six major ice ages occurred when the atmospheric CO2 content was up to 1000 times higher than at present and for half of Earth's history CO2 has been sequestered naturally into algal reefs, coral reefs, sediments, altered rocks, bacteria, plants, soils and oceans.
(SH) Irrelevant what happened in the distant past when the oceans, continents had very different configurations compared to the present.
(IP)This process is still taking place. Ice core drillings show that over the last 400,000 years, CO2 peaks at least 800 years after temperature peaks.(SH). Irrelevant. This was predicted before we had the ice core data. CO2 acts as an amplifier (feedback) during glacial-interglacial transitions when warming (orbital forcing) warms the oceans, permafrost etc, producing C02 outgassing, methane release and changes to biogeochemical cycles. Orbital forcing alone is insufficient to terminate glaciation. C02 is acting as a forcing now. The physics is the same but the timing is different. How would IP explain the termination of glaciations?
(IP)The hypothesis that high atmospheric CO2 drives global warming is therefore invalid. The Earths atmospheric CO2 initially derived from volcanic degassing. Much of it still does and the rest is recycled CO2 from the oceans, rocks and life.(SH). Nonsense. Answered above.
(IP)The claim that warming will increase in the future has been disproved by the climate modellers’ own data. Climate models of the 1990s did not predict the El Nino of 1998 or the cooling in the 21st century.
(SH). Nonsense. Climate models aren’t supposed to predict stochastic events! Either IP doesn’t understand how models work (in which case he shouldn’t pontificate about them) or he is deliberately misunderstanding them. There has been no cooling in the 21st century.
(IP) If such models are inaccurate only 10 years into the future, how can they be accurate for longer-term predictions? Furthermore, when these models are run backwards, they cannot be used to identify climate-driving processes involving a huge transfer of energy (eg, El Nino), volcanoes, solar changes and supernovae.(SH) It’s worth saying that models have predicted an enormous amount. They correctly predicted the cooling from Pinatubo; stratospheric cooling and troposphere warming; arctic amplification; warming of the land compared with the oceans; enhanced warming at night etc.
(IP)Climate models tell us more about the climatologists than they do about nature.(SH) I don’t understand. Not many climatologists I know require the solution of partial differential equations to explain their behaviour. On second thoughts…..
(IP)Another claim is that climate cannot be reversed. This invokes a non-dynamic planet. The fact that previous warmings with an atmospheric temperature some 5 degrees C higher than now (eg, Minoan, Roman, Medieval) were reversed is conveniently ignored, as are the great climate cycles driven by the Sun, supernovae, the Earth’s orbit, tectonics and tides seen on modern, archaeological and geological time scales.(SH) I don’t understand the ‘reverse’ bit here. Past warming (Holocene at least) was not global and T were not as high as today. The 5 degrees bit is nonsense.
(IP)“Tipping points” are another sensationalist unsubstantiated claim. In past times when atmospheric CO2 and temperature were far higher, there were no tipping points, climate disasters or runaway greenhouse.
(SH) terms like ‘climate disasters’ and ‘runaway’ are emotive….no scientists use these (at least not in the scientific literature). Is IP saying that threshold responses have not occurred in the past? If he is, then he’s wrong.
(IP)The climate catastrophists attempt to create fear by mentioning the carbon cycle but just happen to omit that significant oxygenation of the atmosphere took place when the planet was in middle age and this process of photosynthesis resulted in the recycling and sequestration of carbon.(SH) Irrelevant to the present day.
(IP)The atmosphere now contains 800 billion tonnes (800 Gt) of carbon as CO2. Soils, vegetation and humus contain 2000 Gt of carbon in various compounds, the oceans contain 39,000 Gt and limestone, a rock that contains 44% CO2, contains 65,000,000 Gt of carbon. The atmosphere contains only 0.001% of all carbon at the surface of the Earth and far greater quantities are present in the lower crust and mantle of the Earth.(SH) Irrelevant.
(IP) Human additions of CO2 to the atmosphere must be taken into perspective. Over the last 250 years, humans have added just one part of CO2 in 10,000 to the atmosphere. One volcanic eruption can do this in a day.(SH) Wrong. The increase is around 30% or so. Volcanic eruptions do not produce as much C02 as humans.
(IP)Climate chestnuts about polar ice are commonly raised. What is not raised is that ice is dynamic; it advances and retreats. While the Arctic is warming, the Antarctic is cooling and vice versa and if ice did not retreat, then the planet would be covered in ice.
(SH). Irrelevant and wrong. Of course ice retreats. It is doing now (the majority of glaciers, GIS, much of the WAIS, ice shelves etc). Antarctica is warming (see Steig et al. 2009).
(IP) For less than 20% of time Earth has had ice. The Antarctic ice sheet has been with us for 37 million years, during which time there were extended periods of warmth and the ice sheet did not disappear. So too with the Greenland ice sheet which has enjoyed nearly three million years of expansion and contraction, yet did not disappear in extended times far warmer than at present.(SH) Irrelevant. No-one is saying that the Antarctic or GIS is going to disappear….a couple of metres sea level rise by the end of the century might have some consequences though!
(IP) Sea level is also dynamic and has risen and fallen over time by at least 600 metres. Since the end of the glaciation 12,000 years ago, sea level rose some 130 metres until 6,000 years ago when it was about 2 metres higher than at present. This is an average sea level rise of more than 2 cm per year. It is now rising at about 1mm per year. This sea level rise has flooded Bass Strait, the English Channel and destabilised the west Antarctic Ice Sheet. It is this sea level rise that has stimulated coral growth, created larger shallow water ecologies and changed the shape of landmasses.(SH) Irrelevant and wrong. Sea level rise is over 3mm per year, not 1mm. With hundreds of millions of people living on the coasts, and major cities located near to sea level, does IP not think that 1-2m of sea level rise by the end of the century will have an effect?
(IP)The fear-mongering suggestion that oceans will become acid is also misleading. The oceans are buffered by sediments and volcanic rocks on the sea floor and even in past times when atmospheric temperature and CO2 were far higher than at present, there were no acid oceans. If there had been, there would be no fossils with calcium carbonate shells. Although industrial aerosols are decreasing, the climate catastrophists omit to state that volcanic aerosols kill. At least three of the five major mass extinctions of complex life on Earth were probably due to aerosols emitted by volcanoes.(SH) Irrelevant. There is compelling evidence that ocean acidification is happening, and will become a major issue.
(IP)If our climate catastrophists want to twiddle the dials and stop climate change, they need to play God and change radiation in the galaxy, the Sun, the Earth’s orbit, tidal cycles and plate tectonics. Once they have mastered volcanoes, then we can let them loose on climate change.(SH) It’s not a question of stopping climate change. It’s a question of stopping the enormous emissions of GHG and the T rise that has to follow. We’ve known about the Greenhouse Effect since the early 19th century. Maybe IP would like to rewrite nearly 200 years of atmospheric physics?
IP) There have not been independent scientific review or financial due diligence on various nation's emissions trading schemes. All that there has been is spin and fear mongering.(SH) This is not science, so no response is required.It is these legislative time bombs across the developed world that will destroy productive industries in rural and industrial areas.

(SH). In the end who to believe? We have well-established physics (since 1824) that shows that there is a greenhouse effect; that C02 is GHG (since 1859); and that doubling C02 would increase T by several degrees (since 1896). If Ian Plimer wants to argue these points then he needs to publish his ideas in the peer-reviewed scientific literature. If he’s right then he will win the Nobel Prize. That he doesn’t do so (nor does any other sceptic) is rather telling!