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Published: September 30, 2013 15:39 IST | Updated: September 30, 2013 15:39 IST

A brief history of climate science

Ed Hawkins

Climate change is often seen as a recent phenomenon, but its roots are actually far older the effects of human activity on the globalclimate have been discussed for more than 150 years.

ByEd Hawkins, University of Reading

Climate change is often seen as a recent phenomenon, but its roots are actually far older the effects of humanactivity on the global climate have been discussed for more than 150 years.

In the 1820s, the French mathematician Joseph Fourier was trying to understand the various factors that affectEarths temperature. But he found a problem according to his calculations, the Earth should have been a ball ofice.

The most obvious factor, the Sun, did not seem to provide enough energy to raise the temperature of Earth abovefreezing. Fouriers initial ideas, that there must be additional energy coming from the Earths core or from thetemperature of outer space, were soon dismissed. Fourier then realised that the atmosphere, which at first seemedtransparent, could be playing a crucial role.

Then, in 1861, the Irish physicist John Tyndall performed an experiment which changed our view of the atmosphere.Tyndall demonstrated that gases such as methane and carbon dioxide absorbed infrared radiation, and could trap

heat within the atmosphere. He immediately realised the implications and remarked that these gases wouldproduce great effects on the terrestrial rays and produce corresponding changes of climate.

Although this discovery would have profound consequences for understanding future climate, Tyndall, like most ofhis colleagues, was primarily interested in understanding the causes of ice ages, which had been discovered in 1837

byLouis Agassiz.

What was missing however was an estimate of how much these gases could warm or cool the planet. SvanteArrhenius, a Swedish chemist, provided the first numerical estimates of climate sensitivity defined as thetemperature change corresponding to a doubling of carbon dioxide in the atmosphere. He suggested a value around4C in 1896.

While the scientists continued to debate the causes of the ice ages, the Earth was warming. From the 1920s onwards

ToastyKenThe future of the globe used to look a lot brighter.

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meteorologists began to realise that the climate of various regions had changed. Joseph Kincer suggested in 1933that temperatures in individual cities had been rising. At the same time, others had started measuring carbondioxide in the atmosphere. But, it took an amateur meteorologist to put the puzzle together.

Guy Stewart Callendar was a steam engineer who was fascinated by the weather. He meticulously collectedtemperature records from around the world, examined the carbon dioxide measurements and studied the work of

Arrhenius and others. In his spare time, and without the aid of a computer, he performed the tedious calculationsrequired to measure the temperature of the planet. These efforts produced the first evidence that Earths surface was

warming.

Exactly 75 years ago, in 1938, Callendar delivered his analysis to the Fellows of the Royal Meteorological Society. Herevealed evidence for a 0.3C rise in global temperatures over the previous 50 years and suggested that this waslargely due to the increase in atmospheric carbon dioxide from fossil fuel burning. His findings were found to beinteresting, but were not viewed as conclusive by the esteemed Fellows.

Undeterred, Callendar continued his research, gathering additional evidence. In later years he published the firstestimates of the change in carbon dioxide over time, prompting Charles Keeling to set up the first dedicatedobservatory for measuring gases in the atmosphere.

In 1961, Callendar updated his estimates for global temperatures with more observations, and these agreeremarkably well with our current understanding. Callendar also felt that a warmer climate would be beneficial as it

would delay the return of the deadly glaciers and allow crops to be grown at higher latitudes.

In the 75 years since Callendars discovery that carbon dioxide was warming the planet, much more has been learnt

about the climate. But the basic picture has not changed. We are now more confident than ever of the role of humanactivity on global temperatures. We also have a more complete understanding of the consequences of a warmerplanet.

With all the attention on the IPCCs 5th Assessment Report in 2013, the considerable efforts of Callendar and hiscontemporaries in advancing our understanding of the climate should not be forgotten.

Ed Hawkins receives funding from the UK Natural Environment Research Council. He is affiliated with the UKNational Centre for Atmospheric Science.

This article was originally published at The Conversation. Read the original article.

Keywords: Svante Arrhenius, climate change, history, global warming, Joseph Kincer, Charles Keeling, John

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