Earlier this year, the UN’s International Energy Agency (IEA) announced unpublished estimates of global emissions for 2010, showing a record increase of just under 6%. Now, the US Department of Energy’s CDIAC has released its own preliminary estimate of 5.9% for emissions due to fossil-fuel combustion and cement-making.

Until 2008, global emissions were rising about 3% annually - at or above the IPCC’s worst case scenario. 2009, thanks to the GFC, was a reprieve, but that has now been neutralized by easily the largest annual increase ever.

A bit less than half the growth came from China, now by far the world’s biggest emitter, with emissions growth last year of 10%. At the same time, Mauna Loa observatory reported a rise for the year in global mean atmospheric CO2 concentration of 2.3 ppmv (parts per million by volume) compared to the decade average of 1.95 ppmv.

There’s something riveting about these numbers that I want to try and share with you. Learning about them brought me a feeling like fear - a visceral, spine-chilling sensation, and the thought that we might have to explain to our grandkids that we didn’t even try very hard to fix this for them: we just couldn’t get organized and didn’t really care enough.

Why is 6% a scary number? Why does the idea of telling this to the grandchildren seem so loathsome, so irresponsible, so tragic? A short answer is: blindness. Experts have been telling us that, if we are to manage this problem of a disrupted climate, we have to be reducing emissions by about 6% annually all the way to zero. Each year we increase them, two things happen, the required reduction rate for any given peak concentration goes up; and the risk of triggering amplifying feedbacks rises. Delaying a halt to emissions growth means a higher eventual peak and a much harder job getting them back to nothing.

Somehow, we’ve become used to a cautious public rhetoric which speaks of chances and possibilities and long-term effects with a remote sound to them. But this is very misleading. It’s true that senior people alive today will not live to see the unravelling of our economic infrastructure or the loss of whole ecosystems - that will be for our descendants to mourn - but we can foresee these things. They’re not vague shadows but clear and calculable consequences of what we are doing now. 6% tells us our leaders have turned away from what we certainly know, to focus on what they know - that is, doing things the way they’ve always done them. They are not bad men or monsters. They must have persuaded themselves they’ll not be the ones reporting to the grandkids in some future decade; and they’re probably right. Posthumous chagrin doesn’t hurt.

But they are also profoundly and tragically wrong. Responsibility doesn’t die with the perpetrator. Many excuses will be made (you could probably write them all out now) but none of them - not one - will be just. We know everything we need to accurately diagnose our problem and institute a remedy. We’re the first people on Earth who faced an ecological emergency with these advantages. So ignorance cannot be an excuse. It will be pleaded that our international institutions were too primitive to command the required cooperation. But this is simply to say that we couldn’t cooperate because we’re used to competing - as if we couldn’t be compelled by any knowledge, no matter how grave.

It will certainly be said that the present commercial interests of some groups prevailed over the welfare of future people - and that will be true and a terrible indictment - but it will not excuse us one bit. And it will be remembered that a conflict of ideas grew up - a kind of phony war between the scholars who discovered the problem and undertook to warn us, and a reactionary group who found these facts intolerable. Ordinary folks, it will be said, grew confused by the tirade, and politicians who might have backed the necessary measures became timid and confused too. If there are any genuine villains in this sad story it is these people - the inventors and distributors of lies - and the businessmen who held hands with them.

6% is a measure of their success. No one wants to see their grandkids suffer. So if we’d been informed all along by expert scientists and officials, rather than muddled by propagandists, it’s hard to believe we’d not have done more towards an effective remedy already. 6% means an extra 1.4 billion tonnes of CO2 added to what we must sooner or later get rid of. Let there be no doubt whatsoever, the only way to give our descendants a natural heritage anything like the one we’ve known is to bring atmospheric CO2 back to 350 ppmv or a bit less - the level that can return the Earth close to energy balance by century's end. Every year we push it in the opposite direction we make this harder.

Here’s the situation we face. Burning fossil-fuels and making cement injected 33.5 billion tonnes of CO2 into the air in 2010 (deforestation and land use added the equivalent of about another 10 billion tonnes). That is way too much for the terrestrial carbon cycles to soak up. Roughly half of it goes into the ocean; most of the rest stays in the air, augmenting the greenhouse forcing. If we continued to increase emissions by 6%, by 2015 the contribution from fossil fuel and cement would be 44 billion tonnes, and the annual incremental rise of CO2 concentration would be close to 3 ppmv. That’s the year Kevin Anderson identified as the latest we could turn around emission increases to have any chance of a peak CO2 of 450 ppmv. There’s nothing magic about 450 - but it’s been used a lot as a sort of barrier between manageable and dangerous futures. Nobody can have any doubt that if emissions grow at 6% for another five years instead of falling, we’d be committed to a much higher peak than that - closer to 800, maybe more.

Could we pull down a peak of 800 ppmv in a century or two? Nobody has any idea - it is so far from anything familiar, about all we can say is that it looks incredibly dangerous. Last time the air held that much CO2 was around 50 million years ago. That’s worth repeating: 50 million years. We wouldn’t recognize our planet. Not many creatures we know were alive & it’s impossible to say whether humans could survive in a civilized state in such a world. The hazards some of us worry about now - floods, storms & droughts would hardly matter because the productivity of every ecosystem and every physical environment would be so altered that every single aspect of our arrangements for sustaining ourselves would be obsolete.

It is a great shame that reticence prevents many scientists from speaking publicly about their fears for the future. A cancer specialist cannot say with certainty how long a patient will live. Nonetheless we don’t find it remarkable that these experts routinely do make prognostic judgements - indeed we expect them to do so, because while nobody can do it perfectly, no one does it better. In the same way, the incomplete science of climate isn’t in any position to reveal the detailed future - yet the best judgements of the best practitioners are still valuable - and the best we can have. We know now from experience that at a certain level of generality, a great deal can be said about the future, and in private most scientists are extremely concerned. Those who do speak to inform the wider public couldn’t be plainer: “emissions must be on a downward trajectory within a decade”, they say, or we could easily trigger amplifying feedbacks that will make things uncontrollable.

How can we tell the grandkids that?