Our world was hotter 1,000 years ago

Climate change, or global warming, is the most controversial topic in the world today, and the debate shows no signs of calming down.

Climate change, or global warming, is the most controversial topic in the world today, and the debate shows no signs of calming down. Climate change scientists have become embroiled in a fresh controversy over a claim that

Himalayan glaciers could disappear by 2035. The claim was contained in a wide-ranging report produced in 2007 by the Intergovernmental Panel on Climate Change (IPCC), a body made up of the world?s leading climate change scientists that advises governments.

The IPCC published the following statement in its fourth assessment report: ?Glaciers in the Himalaya are receding faster than in any other part of the world and, if the present rate continues, the likelihood of them disappearing by the year 2035 and perhaps sooner is very high if the Earth keeps warming at the current rate.? The statement came nearly verbatim from an article published in Down to Earth on April 30, 1999. There were several problems with this piece. For example, it attributed the claim that that total glacier area would shrink ?from the present 5,00,000 to 1,00,000 square km by the year 2035? to former International Commission for Snow and Ice president VM Kotlyakov. But Kotlyakov?s report had referred to all glaciers outside the polar regions (not just in the Himalayas) and more importantly it had referred to 2350?not 2035. Further, Kotlyakov?s report specifically said glaciers will survive in the Himalayas even then.

Climate change scientists say the 2035 claim said was only a minor detail in a report that was thousands of pages long and drew on data from thousands of sources. The Himalayan claim was not included in the key document arising from the report, such as the summary for policymakers that was presented to governments to help them draft a response to the problem of global warming.

From East Anglia to Sarah Palin

But the claim is another embarrassment for climate change scientists, who were already on the defensive after a series of e-mails were published late last year that appeared to show some scientists planning to refuse access to their data, and adjusting the presentation of their data to emphasise the dangers of climate change. The e-mails, hacked from the servers of the University of East Anglia, generated fierce criticism of the scientists just before the Copenhagen conference on climate change last December. Climate change sceptics argued that the leaked e-mails showed flaws in the practices of climate scientists, and damaged the credibility of their conclusions. Climate scientists responded that the e-mails were taken out of context, and did not show serious attempts to manipulate scientific conclusions.

In the US, a former vice-president and a former vice-presidential nominee have engaged in a public battle over climate change, a tiff sparked by Sarah Palin?s oped piece in the Washington Post and furthered by Al Gore?s rebuttal on MSNBC. The former Alaska governor charged that leading climate experts have ?destroyed records, manipulated data to ?hide the decline? in global temperatures, and tried to silence their critics by preventing them from publishing in peer-reviewed journals?. Palin was referring to the University of East Anglia controversy. She wrote that she had personally witnessed ?the impact of changing weather patterns?. But ?while we recognise the occurrence of these natural, cyclical environmental trends, we can?t say with assurance that man?s activities cause weather changes?. Palin also took to Facebook to allege that concerns over global warming are ?doomsday scare tactics pushed by an environmental priesthood?.

Gore rebutted that the scientific community has worked intensively on the issue for 20 years. ?It?s a principle in physics? It?s like gravity, it exists.?

Further back in history

It?s clear that the world was warmer during medieval times. By mapping the data published (all peer-reviewed) by 752 individual scientists from 442 separate research institutions across 41 different countries, and correlating their comparisons of temperatures changes since medieval times, after factoring in the fact that these studies use a range of ice cores, stalagmites, sediments and isotopes, we find that temperatures were about 0.5?C warmer worldwide.

Prior to IPCC?s third assessment report of 2001, the accepted depiction of the prior millennium?s warmth was that published in the panel?s 1990 maiden assessment? global temperatures had fluctuated drastically over the period. And data derived from sources including tree-rings, lake sediments, ice cores and historical documents bear out that position. Indeed, it?s abundantly evident that since the last glacial period ended, over 14,000 years ago, the Earth?s climate has undergone multi-century swings from warming to cooling that occur often and with remarkable rapidity. And not one but three such radical shifts occurred within the past millennium.

The years 900-1300 AD have been labelled the Medieval Warming Period, as global temperatures rose precipitously from the bitter cold of the previous epoch?the Dark Ages?to levels several degrees warmer than today. A sudden period of cooling then followed and lasted until the year 1850. This Little Ice Age brought on extremely cold temperatures, corresponding with three periods of protracted solar inactivity, the lowest temperatures coinciding with the quietest of the three (The Maunder Minimum 1645-1710). And then began the modern warming period, which, by the way, many scientists believe ended with the millennium itself.

Given these natural shifts over the past 1,000 years, it?s certainly not surprising that after a period of cooling, which followed a period of warming, we?d again enter a period of warming. And that, of course, presented quite the quandary to opportunists hell-bent on blaming warming on industrial revolution-triggered atmospheric CO2 increases. Something had to be done to convince the world that modern warming was unprecedented and could therefore only be explained by something unnatural, specifically ?the greenhouse effect. And something was indeed done.

Hockey stick graph and its wonders

In 1995 everyone agreed the world was warmer in medieval times, but CO2 was low then and that didn?t fit with climate models. In 1998, suddenly Michael Mann ignored the other studies and produced a graph that scared the world (what infamously began to be known as the hockey stick graph?tree rings showing that the ?1990s was the hottest decade for a thousand years?. Now temperatures exactly ?fit? the rise in carbon! The IPCC used the graph all over their 2001 report. Government departments copied it. The media told everyone.

The chart is relatively flat from 1000 to 1900 AD, indicating that temperatures were relatively stable for this period of time. The flat part forms the stick?s ?shaft?. After 1900, however, temperatures appear to shoot up, forming the hockey stick?s ?blade?. The combination of the two in the chart suggests a recent sharp rise in temperature caused by human activities. But the graph?s author, Michael Mann, was reluctant to provide his data or methods?normally a basic requirement of any scientific paper. It took legal action to get the information that should have been freely available.

Within days, Steven McIntyre showed that the statistics were so flawed that you could feed in random data, like stock prices, and still make the same hockey stick shape nine times out of ten. Mann had left out some tree rings he said he?d included. If someone did a graph like this in a red herring stock prospectus, he could invite legal action.

In the United Nations Environment Programme?s Climate Change Science Compendium 2009, the eco-plea opens with the following words from UN Secretary-General Ban Ki-moon: ?The science has become more irrevocable than ever: Climate change is happening. The evidence is all around us. And unless we act, we will see catastrophic consequences including rising sea levels, droughts and famine, and the loss of up to a third of the world?s plant and animal species.? A striking chart in support of this argument attempts to plot atmospheric CO2 concentrations and mean global temperature during the past millennium. It looks vaguely familiar, because it?s Mr Hockey Stick again?apparently having sat for a bit of a makeover.

What if we confront the fact that temperatures were higher 1,000 years ago, and cooler 300 years ago. The Earth started warming long before cars and power stations were invented. There?s little correlation with CO2 levels. It is instructive to note that the mean temperature as of November 2009 is 0.5?C above the baseline.

Some believe mere graphic tricks are being used to fool people into believing in anthropogenic global warming. And facts suggest a steady long-term temperature rise that began long before the industrial era (late 20th century) that Warmists demonise.

The author is a Wharton Business School MBA and CEO, Global Money Investor

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First published on: 29-01-2010 at 22:05 IST