We can thank our clouds for saving us from a fate worse than Venus's

Clouds are essential as they reflect and scatter sunlight back into space - but nobody knows how hot the planet can become before the clouds no longer help us.

No one wants to think about cloudy skies in August but if they’re up there, be grateful. According to research published in Nature Geoscience on 28 July, we can thank clouds for saving us from a fate worse than Venus’s.

Venus – a barren, hot planet – suffered from the “runaway greenhouse effect” when its temperature rose past a critical point. That, it seems, arose from having too much thermal insulation resulting from the heat-storing greenhouse gases in the planet’s atmosphere.

On Venus, as on earth, carbon dioxide was an important contributor. Our planet is wet and heating it creates a lot of water vapour, a far more potent insulator than carbon dioxide. The more water vapour there is, the faster warming occurs.

Once you hit the point of no return at which the runaway effect starts, it would take only a few thousand years for life on earth to become untenable.

The recently published calculations show that the Venus effect could happen here – if it weren’t for clouds. They look white and fluffy to us because they scatter light. The tops of the clouds do the same, scattering and reflecting sunlight back into space before it has the chance to warm the earth and take it into the runaway scenario.

There’s still some uncertainty in the calculations, however: we don’t know exactly how hot we can let the planet become before the clouds can no longer help us. Unfortunately, uncertainty in other areas is pushing us in the right direction to find out.

The Intergovernmental Panel on Climate Change (IPCC) will publish its fifth assessment report next year. A draft report of some of its data, leaked to the Economist, suggests that increasing carbon-dioxide levels won’t warm the atmosphere as much as we had previously thought. In 2007, the IPCC stated that concentrations of between 445 and 490 parts per million (ppm) of carbon dioxide were likely to result in a rise in temperature of 2° to 2.4° Celsius above the temperatures before the Industrial Age. The new data suggests that 425 to 485ppm would give a rise of 1.3° to 1.7° Celsius.

The Economist threw in plenty of caveats (“The two findings are not strictly comparable”; the data comes “from a draft version of the report, and could thus change”) but evidently felt the burden of reducing carbon emissions is not as onerous as it once seemed. “It is clear,” the paper declared, “that some IPCC scientists think the projected rise in CO2 levels might not have such a big warming effect as was once thought.”

As it turns out, it’s not just carbon dioxide that we need to worry about. US researchers have been mapping the gas leaks from pipelines in urban areas. Boston has more than 3,000 leaks in the pipelines that deliver gas to homes and industries. Preliminary data from Washington, DC indicates that the capital is just as prone to leaks. It’s of huge concern because methane is 25 times more potent as a greenhouse gas than carbon dioxide. If similar figures apply to every other major city with an ageing gas infrastructure, perhaps the chances of earth slipping into a runaway greenhouse effect need revising upwards.

We can be sure those figures won’t be in the IPCC report, however. As for the ones in the Economist, we’ll just have to wait and see. In many ways, it doesn’t matter: the numbers are out there now and will be put to work by those keen to make sure we don’t punish carbon emitters. Such a leak is not going to make governments feel inclined to do something about the problem – they can just keep their head in the clouds.

Sunset over Tiananmen Square after a day of heavy pollution in Beijing. Photograph: Getty Images.

Michael Brooks holds a PhD in quantum physics. He writes a weekly science column for the New Statesman, and his most recent book is At the Edge of Uncertainty: 11 Discoveries Taking Science by Surprise.

This article first appeared in the 12 August 2013 issue of the New Statesman, What if JFK had lived?

Photo: Getty
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Jeremy Corbyn sat down on train he claimed was full, Virgin says

The train company has pushed back against a viral video starring the Labour leader, in which he sat on the floor.

Seats were available on the train where Jeremy Corbyn was filmed sitting on the floor, Virgin Trains has said.

On 16 August, a freelance film-maker who has been following the Labour leader released a video which showed Corbyn talking about the problems of overcrowded trains.

“This is a problem that many passengers face every day, commuters and long-distance travellers. Today this train is completely ram-packed,” he said. Is it fair that I should upgrade my ticket whilst others who might not be able to afford such a luxury should have to sit on the floor? It’s their money I would be spending after all.”

Commentators quickly pointed out that he would not have been able to claim for a first-class upgrade, as expenses rules only permit standard-class travel. Also, campaign expenses cannot be claimed back from the taxpayer. 

Today, Virgin Trains released footage of the Labour leader walking past empty unreserved seats to film his video, which took half an hour, before walking back to take another unreserved seat.

"CCTV footage taken from the train on August 11 shows Mr Corbyn and his team walked past empty, unreserved seats in coach H before walking through the rest of the train to the far end, where his team sat on the floor and started filming.

"The same footage then shows Mr Corbyn returning to coach H and taking a seat there, with the help of the onboard crew, around 45 minutes into the journey and over two hours before the train reached Newcastle.

"Mr Corbyn’s team carried out their filming around 30 minutes into the journey. There were also additional empty seats on the train (the 11am departure from King’s Cross) which appear from CCTV to have been reserved but not taken, so they were also available for other passengers to sit on."

A Virgin spokesperson commented: “We have to take issue with the idea that Mr Corbyn wasn’t able to be seated on the service, as this clearly wasn’t the case.

A spokesman for the Corbyn campaign told BuzzFeed News that the footage was a “lie”, and that Corbyn had given up his seat for a woman to take his place, and that “other people” had also sat in the aisles.

Owen Smith, Corbyn's leadership rival, tried a joke:

But a passenger on the train supported Corbyn's version of events.

Both Virgin Trains and the Corbyn campaign have been contacted for further comment.

UPDATE 17:07

A spokesperson for the Jeremy for Labour campaign commented:

“When Jeremy boarded the train he was unable to find unreserved seats, so he sat with other passengers in the corridor who were also unable to find a seat. 

"Later in the journey, seats became available after a family were upgraded to first class, and Jeremy and the team he was travelling with were offered the seats by a very helpful member of staff.

"Passengers across Britain will have been in similar situations on overcrowded, expensive trains. That is why our policy to bring the trains back into public ownership, as part of a plan to rebuild and transform Britain, is so popular with passengers and rail workers.”

A few testimonies from passengers who had their photos taken with Corbyn on the floor can be found here