So, one might ask oneself, just how urgent is our climate change situation? Surely it’s not, you know, time to panic or
The world is close to reaching tipping points that will make it irreversibly hotter, making this decade critical in efforts to contain global warming, scientists warned on Monday.
Scientific estimates differ but the world’s temperature looks set to rise by six degrees Celsius by 2100 if greenhouse gas emissions are allowed to rise uncontrollably.
As emissions grow, scientists say the world is close to reaching thresholds beyond which the effects on the global climate will be irreversible, such as the melting of polar ice sheets and loss of rainforests.
“This is the critical decade. If we don’t get the curves turned around this decade we will cross those lines,” said Will Steffen, executive director of the Australian National University’s climate change institute, speaking at a conference in London.
For ice sheets – huge refrigerators that slow down the warming of the planet – the tipping point has probably already been passed, Steffen said. The West Antarctic ice sheet has shrunk over the last decade and the Greenland ice sheet has lost around 200 cubic km (48 cubic miles) a year since the 1990s.
Most climate estimates agree the Amazon rainforest will get drier as the planet warms. Mass tree deaths caused by drought have raised fears it is on the verge of a tipping point, when it will stop absorbing emissions and add to them instead.
Around 1.6 billion tonnes of carbon were lost in 2005 from the rainforest and 2.2 billion tonnes in 2010, which has undone about 10 years of carbon sink activity, Steffen said.
One of the most worrying and unknown thresholds is the Siberian permafrost, which stores frozen carbon in the soil away from the atmosphere.
“There is about 1,600 billion tonnes of carbon there – about twice the amount in the atmosphere today – and the northern high latitudes are experiencing the most severe temperature change of any part of the planet,” he said.
In a worst case scenario, 30 to 63 billion tonnes of carbon a year could be released by 2040, rising to 232 to 380 billion tonnes by 2100. This compares to around 10 billion tonnes of CO2 released by fossil fuel use each year.
Once again, let me remind you, dear readers, that the permafrost number we see quoted all the time is 1,600 billion tons of carbon, not CO2. Even making the generous assumption that whatever portion of that carbon is liberated turns into CO2 and not the much more problematic (in the short run) CH4, then we’re talking about a total store of 5.9 trillion tons of CO2 equivalent. Liberating even 0.1% of that each year, far less than the figures speculated about above, would add about 5.9 billion tons of CO2 to the atmosphere, or almost exactly the net greenhouse gas emissions of the entire US for 2010. So, as we struggle to make incremental reductions in our global emissions (which are still rising, despite our decidedly sub-optimal efforts), imagine adding an additional US, emissions-wise, to the equation every year. That would require the entire world to wipe out all of our emissions in a very short time frame to avoid a nightmarish outcome. And you thought “80% below 1990 levels by 2050″ was a really tough prescription.
Before the Usual Suspects start claiming I’m being “alarmist”, let me explicitly point out that I’m not saying the liberation of any specific percentage of the Arctic carbon is a sure thing, but we do know that thanks to the albedo flip that region is warming much faster than the places where most of us live. And as someone (Richard Alley?) once pointed out so eloquently in a Congressional hearing, “it gets warm… ice melts”. So there is surely at least some CO2 and CH4 being released from the Arctic permafrost; like so many other critically important details in climate science we simply don’t know with any confidence how much or how it will change with just a bit more warming. We haven’t seen a smoking gun signal in the global atmospheric CO2 numbers, so there’s nothing “big” happening on this front yet. Similarly, we’ve had reports of CH4 releases from Siberian hydrate deposits, but those emissions don’t seem to be enough to move the needle on the global figures. Considering the uncertainty and the potential for a massive warming surge from either of those sources, this is about as close to playing Russian Roulette with our future as one could imagine.
I would also point out that the article above refers to the legendary 2C line separating “some warming” from “catastrophe”, or however you’d care to phrase it. This is a highly dubious way to view our situation simply because there’s precious little hard evidence that we can warm the biosphere by 2C and not cause immense human suffering. If anything, the evidence is accumulating that the earth system is more sensitive to disruption than thought, with more change per unit of warming and more amplification from reinforcing feedbacks than expected. There has been an effort to use a guideline of 1.5C (at an atmospheric CO2 content about 40ppm below our current level) instead of 2C, but it seems highly doubtful that the major emitting countries will agree to that reformulation, as it’s simply too hard.
Bonus points for anyone who read the title of this post and instantly flashed back to Robert Palmer’s “Simply Irresistible” video, which should have won a special Grammy for the dancers. As the song says, “She’s so fine, there’s no telling where the money went” — nope, no way to see that as a metaphor for our climate situation…
 If you want to assume some of it will be methane, which it surely will, then take that portion of the 5.9 trillion tons and multiply it by 20 or 25 to account for the greater global warming potential of CH4. Consider this a warning: It doesn’t take much number fiddling before you can scare yourself spitless.
 The actual US number is 5.823 billion tons. See Table ES-2 in the US EPA’s 2012 Draft U.S. Greenhouse Gas Inventory Report.
 Perhaps you’ve heard of the main group pushing this idea? Does “350.org” ring a bell?