Dr Willem de Lange:

In 1996 the United Nations Intergovernmental Panel on Climate Change’s (IPCC) Second Assessment Report was released, and I was listed as one of approximately 3000 “scientists” who agreed that there was a discernable human influence on climate.

I was an invited reviewer for a chapter dealing with the economic impact of sea level rise on small island nations. In keeping with IPCC procedures, the chapter was written and reviewed in isolation from the rest of the report, and I had no input into the process after my review of the chapter draft.
I was not asked if I supported the view expressed in my name, and my understanding at the time was that no evidence of a discernable human influence on global climate existed.

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The inconvenient truth that is generally ignored, is that the atmosphere is not capable of warming the oceans to any significant degree – 99.9 percent of ocean heat is derived from sunlight at wavelengths less than 3 microns. The balance is mostly from heat leaking from the interior of the Earth. The Greenhouse Effect involves a delay in the loss of infra-red radiation at wavelengths greater than 5 microns.

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What does this mean for climate change? It means that variations in the amount of sunlight reaching the oceans will control the rate at which the oceans warm. This is influenced at long time scales by changes in the Earth’s orbit. At short time scales there are changes in the amount of sunlight associated with the sunspot cycle. These changes are small, but due to the ability of the oceans to store heat it may be possible to have a cumulative effect as sunspot cycles wax and wane. However, the main control is the amount of cloud and ice cover. Clouds and sea ice reflect sunlight before it can be absorbed by the oceans, and is referred to as albedo. Albedo changes have a greater influence on climate than the Greenhouse Effect, and are usually invoked to produce the catastrophic consequences of “Climate Change” (aka Accelerated Global Warming).

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What does this have to do with the 20th Century? Well the observed climate change is consistent with variations in albedo and associated ocean warming and cooling, suggesting that it is just a natural cycle. This pattern of behaviour is evident in palaeoclimate data for most of the last 10,000 years. None of this is simulated in climate models. Instead they focus on the 20th Century increase in CO2, CH4 and a few other greenhouse gases. The increasing concentrations correlate well with global temperature. This is taken as proof that the greenhouse effect is driving temperature.

However, it is also correct that changing ocean temperatures affect the concentration of these gases in the atmosphere. At annual and 2-7 year time scales it is clear that the concentration of CO2 in the atmosphere is strongly driven by the ocean. At longer time scales it is also clear that the concentration of greenhouse gases lags behind, and therefore is driven by, temperature. Once again the oceans are the likely control on atmospheric greenhouse gas concentrations. The IPCC position requires that for 50-100 year periods everything works in reverse, which still showing an oceanic influence at shorter time periods. It is more likely that the warming of the oceans since the Little Ice Age is a major contributor to the observed increase in CO2. Carbon isotopic ratios indicate that while there is a contribution from the burning of fossil fuels, it is of the order 1-5 percent of the increase.

So, I am a climate realist because the available evidence indicates that climate change is predominantly, if not entirely, natural. It occurs mostly in response to variations in solar heating of the oceans, and the consequences this has for the rest of the Earth’s climate system. There is no evidence to support the hypothesis runaway catastrophic climate change due to human activities.