We have a problem. I’ve known we’ve had a problem for a long time. It’s only in the last few years though, after I left my career in engineering to take a PhD in glaciology, studying the changing Greenland ice sheet, that the magnitude and timeframe has become clear. It is now all but impossible to limit global warming, the warming of mean surface air temperature, to less than +2°C from pre-industrial temperatures [1, 2]. Understand also that temperatures over land rise more than this global average, and extremes are likely to be further exaggerated by positive feedbacks. All but impossible because to have even a fifty-fifty chance of keeping warming below that somewhat arbitrary threshold, global greenhouse gas emissions would have to peak within the next five years or so then fall rapidly for decades: “…the threshold of 2°C is no longer viable” .
This fall in emissions would have to happen against the trends of increasing wealth in growing economies and growing populations. Recent history, even with the largest economic slowdown in decades, offers us no hope as global emissions are currently rising faster than ever . It is a fantasy to suggest that the global community is able to collectively choose to peak and decline emissions within the next few years.
The lack of action is not for lack of knowledge. The data and scientific understanding have been clear for a long time and yet over the last decade carbon emissions have increased by a greater amount than in any previous decade (between 2002 and 2011 emissions increased by 2.5 GtCyr-1 from 7.0 to 9.5 GtCyr-1 ). There is nothing in the data to suggest that we have recognised the seriousness of our situation. In fact the reverse is true: we are accelerating into disaster faster than the scientific community thought possible even a decade ago.
As a scientist, I’m not supposed to use emotive words like disaster; however, that is what we are facing - an avoidable disaster of our own making. Reticence amongst the scientific community has probably contributed to our civilisation’s inaction. We know enough to say, and importantly to do
more. As I write this, however, my office is quiet, half empty. My colleagues are attending a conference
on the other side of the planet, elevating their carbon emissions to some of the highest in the world.
Two glimmers of hope I held until recently are fading. The first was offered by researchers quantifying the Earth’s endowment of fossil fuels. Their evidence suggested there simply weren’t the hydrocarbon reserves available to greatly perturb the climate system 
. This is the question I explored for my master’s thesis 
a few years ago. However, as extraction of unconventional resources continues to expand and as Arctic melting unlocks probably significant northern reserves, the hope of these resource limits applying any meaningful and timely brake diminishes. Secondly, our emission growth is linked to our economic growth. Without increasing demand from the expanding wealthy population the hydrocarbon reserves will remain unexploited. The threat of economic collapse, in our case linked to unserviceable debts, is familiar and appears plausible at least for developed Western economies. Exactly three years ago I blogged, with evidence, about the economically induced 2008 emissions peak
. The global economy has proved far more resilient than I imagined. In any case, were western economies to collapse, the remaining four fifths of the global population are unlikely to need asking twice before taking up any hydrocarbon supply slack and attempting to resume the emission growth trajectory.
The time for hope is over; it is simply illogical to continue believing that dangerous future climate projections can be mitigated through national and international agreements, or through pro-active action. We now have to consider life in a 4 °C warmer world, described here in a report for the World Bank 
Our global civilisation appears to be facing a protracted period of decline. Most likely this will be due to the damaging impacts of climate change but if, against the odds, we are spared the worst climate impacts it will only be due to decline from crippling energy shortages or global economic collapse. There is no easy way down for our seven, going on nine billion population, not from the height we’ve now reached. The first half of the 21st century is likely to represent a new peak of human civilisation, the first truly global civilisation, eclipsing our species’ many previous peaks. From here, we can only now hope the cost of climbing so high won’t be so damaging as to deny our distant descendants their own future triumphs.
 PriceWaterhouseCoopers, November 2012.
Peters, G. P., Marland, G., Le Quere, C., Boden, T., Canadell, J. G. & Raupach, M. R. 2012. Rapid growth in CO2 emissions after the 2008-2009 global financial crisis. Nature Climate Change
, 2, 2-4.
Boden, T.A., G. Marland, and R.J. Andres. 2012. Global, Regional, and National Fossil-Fuel CO2 Emissions. Carbon Dioxide Information Analysis Center
, Oak Ridge National Laboratory, U.S. Department of Energy, Oak Ridge, Tenn., U.S.A. doi 10.3334/CDIAC/00001_V2012