Despite the clean technology of the past decade, we continue to extract and burn fossil fuels more than ever before

We have far more oil, coal and gas than we can safely burn. For all the millions of words written about climate change, the challenge really comes down to this: fuel is enormously useful, massively valuable and hugely important geopolitically, but tackling global warming means leaving most of it in the ground – by choice. Although we often hear more about green technology, consumption levels or population growth, leaving fuel in the ground is the crux of the issue. After all, the climate doesn’t know or care how much renewable or nuclear energy we’ve got, how efficient our cars and homes are, how many people there are, or even how we run the economy. It only cares how much globe-warming pollution we emit – and that may be curiously immune to the measures we usually assume will help.

There are three facts that tell you all you really need to know about climate science and politics. One: for all the uncertainty about the detail, every science academy in the world accepts the mainstream view of man-made global warming. Two: virtually every government, recognising the profound danger of tampering with the climate that allowed human society to thrive, has agreed the world must limit the global temperature increase to 2C – a level which isn’t by any means “safe” but may be enough to avoid the worst impacts. Three: the amount of warming we will experience goes up roughly in proportion to the total amount of carbon that global society emits – cumulatively.

Here is the rub. Even if we gave up on all the obscure and unconventional fossil fuel resources that companies are spending billions trying to access and just burned the “proven” oil, coal and gas reserves – the ones that are already economically viable – we would emit almost 3tn tonnes of carbon dioxide. No one can say exactly how much warming that would cause, but it is overwhelmingly likely that we would shoot well past 2C and towards 3C or even 4C of warming.

Four degrees might not sound much but at the planetary level it is. It is about the same as the temperature increase observed since the ice age’s “last glacial maximum”, when much of the northern hemisphere was trapped under ice as thick as the world’s five tallest skyscrapers stacked on top of each other. It is impossible to say what changes another three or four degrees would bring, but the impacts could very plausibly include a collapse in global food production, catastrophic droughts and floods, heatwaves and the beginning of ice-sheet melt that could eventually raise the sea level enough to wipe out many of the world’s great cities.

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Impact of climate change: flooding in India. Photograph: Gideon Mendel/Corbis for Actionaid

Sceptics argue that this doomsday scenario might not come to pass – and they are right. If we are lucky, the impact of burning all that oil, coal and gas could turn out to be at the less severe end of the plausible spectrum. But that is hardly reassuring: it’s akin to saying that it is fine to walk blindfolded into a main road since you can’t be sure there are any cars coming. After less than 1C of temperature increase so far, we are already seeing some profound changes, including a collapse in Arctic sea ice coverage more severe than even the most pessimistic predictions from just a few years ago. (Brits secretly hoping for a hotter future, be warned: that collapsing sea ice may have caused the freakish jet stream behaviour that made 2012 the wettest English year on record and obliterated this year’s spring, both mere amuse-bouche for the feast of climate impacts expected in coming decades, even from the carbon we’ve emitted so far.)

Given what is at stake, it is no wonder that governments agree global warming must be stopped. But that is where the common sense ends and the cognitive dissonance begins. Because to have a decent chance of not exceeding the already risky global target, we need to start phasing out fossil fuels now at a fast enough rate to bring down emissions globally by a few percent a year, and continue doing so for decades to come.

Now compare that with what is actually happening. As with the climate, to understand the situation properly it is necessary to zoom right out to see the long-term trend. Doing so reveals something fascinating, worrying and oddly overlooked. As scientists from Lancaster University pointed out last year, if you plot a graph showing all the carbon emissions that humans have pumped into the air, the result is a remarkably clear exponential curve stretching all the way back to the mid-19th century. Zoom back in on the past decade and it is clear that for all the mounting scientific concern, the political rhetoric and the clean technology, nothing has made a jot of difference to the long-term trend at the global level – the system level. The growth rate in total carbon emissions in the past decade, at around 2% a year, was the same as that of the 1850s.