A perspective on doubts

Chinese voices challenging the IPCC’s conclusions should not be taken too seriously, says Jia Hepeng, who argues that the evidence for man-made climate change is watertight.

Extensive media interest in the Intergovernmental Panel on Climate Change (IPCC) has projected the voices of Chinese scholars who question the body’s conclusions beyond the academic sphere. Their doubts, combined with the extensive cold spell this spring, have shaken many people’s confidence in the existence of man-made global warming.

In essence, these scholars believe that the consensus on the cause of global warming neglects natural factors. They say that, viewed in the context of Earth’s extensive lifespan, global warming may be a natural shift. And they insist that the evidence that climate change is man-made is not comprehensive, and thus not persuasive.

It is true that, even today, there is a great deal of uncertainty surrounding climate science. The models that serve as the basis for speculation on future climate change need further improvement. But it is also clear that these doubts are not weighty enough to overthrow a conclusion reached by thousands of scientists.

What is more, current opposition to the IPCC’s work is not based on fresh evidence. Such doubts have surfaced many times in the past 20 years, some of them raised by institutes under the patronage of interest groups such as oil companies.

Some academics refute the climate-change pattern discerned by paleoclimatologist Michael Mann, whose “hockey stick graph” shows a slight cooling trend over the past millennium, followed by the sudden appearance of warming in the twentieth century – a pattern that can only be explained by the sudden increase of greenhouse-gas emissions.

The scholars who oppose the IPCC’s conclusions insist that increased levels of carbon dioxide are not the cause of this sudden warming. This vein of thought is not new – indeed, it appeared as early as Mann’s conclusion was adapted for publication in the IPCC’s third assessment report in 2001.

In 2006, the United States-based National Academy of Sciences (NAS) published a comprehensive and authoritative data evaluation. It concluded that, no matter whether or not there was an overall cooling trend in the last millennium, a little ice age did indeed occur between the fourteenth and nineteenth centuries and, based on observable data, the temperature of the twentieth century was almost certainly the highest of the last millennium. Such a significant phenomenon cannot be explained by variations in Earth’s orbit, solar radiation or volcanic eruption. Increasing emissions of greenhouse gases appears to be the only possible cause.

It is notable that, when NAS published its report, president George Bush was still in the White House and his administration had openly indicated doubts about the IPCC’s conclusions. In this context, it seems unlikely that the NAS report was manipulated by any interest group.

Based on data from the NAS report and other published evidence approved by the international academic community, the IPCC stated in its fourth assessment report, published in 2007, that it was more than 90% certain that greenhouse-gas emissions were causing global warming.

But what about Earth’s natural variations over millions of years? Indeed, there were times that our planet had higher temperatures and a greater concentration of greenhouse gases (though these conditions were not observed, but calculated). Yet this is not strong enough evidence to overthrow the IPCC’s conclusion. Bear in mind that the panel reported only a 90% likelihood that man-made climate change is occurring. For the most part, the data the IPCC relies on cannot account for a timescale of millions of years. Thus, the other 10% may cover the possibility of extreme conditions that appear every ten million years.

However, scientific conclusions need evidence. Explaining away the current warming trend as a natural change that occurs perhaps once an eon is unreasonable and lacks evidence. In fact, in view of currently accessible evidence, there is no credible explanation for the climate change we are now experiencing other than greenhouse-gas emissions. And extreme weather, drought, flooding and hurricanes caused by global warming are appearing in our everyday life more and more frequently.

Other opponents of this conclusion maintain that the data used in the IPCC assessments has focussed mainly on the northern hemisphere and has not sufficiently covered the developing world. And yet these people are unable to find any contradictory data from the unstudied areas. Furthermore, while the IPCC admits that it has ignored some regions, it has discussed the proper application of the current data in those areas.

Moreover, it is important to note that this data collection is in line with normal statistical practice. Most studies are based on typical and effective samples. If statistical analysis required every item in a given category to be examined, then it would be impossible to conduct any work of this nature.

Sometimes we may feel the climate is actually becoming colder rather than warmer. And this year’s relentless cold wave made many suspicious of global warming theories. But regardless of whether or not the harsh winter will modify the warming trend in the long term, one thing is certain: signs of abnormal weather patterns – including prolonged cold spells – are increasingly obvious. And so, perhaps, we should not get ourselves into too much of a tangle about whether or not the degree of warming is exactly that predicted by the IPCC, at least when we are not discussing it for the purpose of pure science.

Realising the urgency of climate change and its connection with greenhouse-gas emissions, the Chinese premier Wen Jiabao set out plans to develop a low-carbon economy in China in this year’s plenary session of the National People’s Congress. The scholars that doubt the science emphasise that, while they question the certainty of climate change, they still support energy efficiency and low-carbon development – neglecting to realise that, if climate change is not an urgent issue and has no connection with greenhouse-gas emissions, then there is no need to support low-carbon development.

While there are still some uncertainties in climate science, disastrous climate patterns are already affecting us in increasing volume. And so, low-carbon development that aims to reduce carbon emissions and fossil-fuel powered energy consumption is a path we have to choose.

Jia Hepeng is editor-in-chief of Science News Bi-Weekly, published by the Chinese Academy of Sciences, and co-founder of the Climate Change Journalists’ Club.

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