The staid, uncontroversial International Energy Agency said last week that we have five years to preserve our present-day climate.
It's generally agreed that warming of more than 2 degrees Celsius risks disaster. Their studies show that most of that is already built in. In the words of Wonk Blog's Brad Plummer:
The key issue here is something known as “infrastructure lock-in.” The coal plants that countries like China and India are constructing right now are going to last another 50 years, at least. The energy-inefficient buildings we’re erecting will stay up for some time. Every gas-guzzling SUV that gets built will likely get sold and then driven for at least a decade. Which is just a way of saying there’s a lag built into our energy infrastructure. It’s not easy to turn off the carbon tap once we edge near 450 ppm.
To the Guardian, the Agency's chief economist put it plainly:
"The door is closing," Fatih Birol, chief economist at the International Energy Agency, said. "I am very worried – if we don't change direction now on how we use energy, we will end up beyond what scientists tell us is the minimum [for safety]. The door will be closed forever."
This amount of warming has been set, by consensus in the IPCC process, but still has its critics. No sooner had the staid research body issued this alarming opinion, than it was attacked on all sides. Deniers whipped out the mockery
If we get to where it’s “irreversible”, we won’t be bothered by them trying to take our bucks to reverse it.
Think about how peaceful that will be without that alarmism
On the scientific side of the issue, Richard Betts, a climatologist who worked on the earth systems chapter of the most recent IPCC report in the UK, also had doubts:
While really bad things may happen at 2 degrees, they may very well not happen either – especially in the short term (there may be a committment to longer-term consequences such as ongoing sea level rise that future generations have to deal with, but imminent catastrophe affecting the current generation is far less certain than people make out. We just don't know.
The thing that worries me about the talking-up of doom at 2 degrees is that this could lead to some very bad and expensive decisions in terms of adaptation. It probably is correct that we have about 5 years to achieve a peak and decline of global emissions that give a reasonable probability of staying below 2 degrees, but what happens in 10 years' time when emissions are still rising and we are probably on course for 2 degrees?
And yet in the next breath, in a comment in the ensuing discussion, Betts revealed the possibility that the atmosphere could warm much more than 2C by 2060, if fossil fuel emissions aren't reduced. Temps could rise twice as much as 2C, or even more:
While much political attention is focused on the potential for global warming of 2◦C relative to pre-industrial, the AR4 projections clearly suggest that much greater levels of warming are possible by the end of the twenty-ﬁrst century in the absence of mitigation. The centre of the range of AR4-projected global warming was approximately 4◦C.
So the tipping point identified by the agency is a) good news, b) maybe bad news, or c) dwarfed by the really bad news.
Let's be realistic about this much: Talking about climate change can be confusing, even to experts.