Jean Jouzel’s Opinion

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Temps de lecture : 3 minutes  

Lomborg maintains that the efforts required by the Kyoto Protocol will not be effective and will cost a great deal to our societies. According to him, such efforts would reduce global warming by only 0.15°C (0.27°F), which would only delay a rise in temperature by 6 years. These figures get straight to the point, but it is worth looking closer at the method behind their calculation. They are based on a climate model which draws upon two scenarios of CO2 emissions. In the reference model, the yearly carbon consumption rises from its current level of 7 billion tonnes to 20.6 billion by the end of the century. In the second scenario, the Kyoto Protocol is adhered to between 2008 and 2012, then carbon emissions return to their previous levels, as seen in the reference model, reaching 19.5 billion tonnes in 2100. Lomborg doesn’t expand on this, but at least he agrees with the scientific community for whom the Kyoto Protocol is seen as only the first step. But he gets carried away in the same paragraph of his book when he states that “from 2050, we will pay 2% of Gross Domestic Product (GDP) in order to reduce carbon gases.” He misleads readers in two ways with this statement. First, how can we imagine that actions limited to the period 2008-2012 could still have an effect nearly 100 years later? Costs quoted by economists of the IPCC correspond to emissions stabilisation objectives, for which most would require levels inferior to 5 billion tonnes of carbon in 2100. Second, Lomborg consistently chooses the higher estimation: based on several scenarios, the IPCC estimates that, among other scenarios, the average reduction in GDP would be at a peak in 2050 (1.5%) and would start to fall in 2100; but most important, in 2010, in the middle of the Protocol enforcement, reduction in GDP could be less than 0.2% amongst the OECD countries. […]

However, we are nowhere near the 2% which, even if it was accurate, would have only delayed world economic development in 2100 by one year… In opposition to the economist is the climatologist, reiterating the absolute necessity to stabilise the greenhouse effect at a level as close as possible to its current state. Let’s consider this a moment. If we follow the path which would lead us to 20 billion tonnes of carbon per year, our climate could be an average of 3°C hotter than today. That may not seem insignificant but in reality it represents at least half of the increase in temperature that the planet has experienced since the last ice-age, and is consequently a significant climatic change. […]

The significant thermal inertia of the oceans would lead to a real time bomb for future generations due to an inevitable rise in sea-levels, partly as a result of water expansion from gradual heating. If there is a 50 cm (19 in.) rise by the end of the century, this pattern will continue in more or less the same way for several centuries, even if the greenhouse effect stabilises. Greenland is a fragile ice-cap at a latitude vulnerable to the largest increases in temperature. Its partial melting could contribute to an increase of one or two metres (3 to 6 feet) by 2050. By this time, sea levels could inevitably rise 4 to 5 metres (13 to 16 feet) due to human behaviour in the 21st century. Because stabilising the situation requires a reduction in emissions, it is mostly human behaviour over the next few decades, until the middle of the century, that will determine sea level rises in the coming centuries. In the context of sustainable development, this is a strong argument for controlling greenhouse gas emissions as quickly as possible through enforcement of the Kyoto Protocol.

It has now been 35 years since I began a thesis on hailstone formation, with the hope that preventative methods against this natural plague were going to be developed rapidly; this was not the case. This example is food for thought. Even though I believe in progress, I do not accept that, in terms of climate, progress alone will repair its own damages. Artificial climate handling, such as controlling the amount of energy we receive from the sun with giant mirrors, spraying aerosols in the atmosphere or modifying clouds characteristics, are simply frightening. Climatologists clearly support the implication of the Kyoto Protocol, and I believe many economists share the same opinion.

Excerpt from « Response to the Sceptics »


Réseau Action Climat- France (RAC) website

July 21, 2004

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