It’s already later than we realize in the struggle to arrest climate change

A recent essay says the most pressing current scientific and political challenge is to avoid what is known as “dangerous” global warming – the point where world temperatures become irreversible.

As there’s a 25-to-30-year lag between greenhouse emissions and the full impact of their warming, current climate chaos is a result of carbon spewed in the late 1970s. The hit from more recent discharges – including China’s coal plants – is but pain yet to come.

So we’re dangerously close already.

Human activity currently generates 7.2 billion tons of carbon, or about 26.4 billion tons of carbon dioxide a year from fossil fuels, according to the Fourth Assessment Report of the UN’s Intergovernmental Panel on Climate Change.

While transport is one of the fastest growing culprits, it accounts for only 14% of CO2 and other emissions from human activity. Other major sources are electrical power (28.5%), deforestation (18%), industry (14%), and agriculture (14%).

Paul Brown, in Global Warming: The Last Chance for Change , says we are already committed to a further 0.7 degrees C, which would add up to 1.5 degrees C above pre-industrial levels. At that point 18% of the world’s species will die, and 400 million more people worldwide will be threatened by flooding.

It gets worse. As Earth warms, “feedbacks” occur. As Arctic ice melts, there will be less to reflect heat, warming further, melting more, and so on. Were Earth to get roughly 2 degrees warmer than pre-Industrial times, melting polar ice could become irreversible with global warming surpassing the human capacity to control the process. There is a fair chance of reaching 2 degrees if greenhouse gases are allowed to build up to roughly 450 ppm of CO2, just 75 more units.

Some say we have barely 20 years to prevent dangerous global warming. The Stern Review puts the date at 2035, while James Hansen of NASA’s Goddard Institute for Space Studies has said we have until 2015.

Given the magnitude of the problem, there is a very short time available to arrest it. It’s crucial for the U.S. and Canada to stop waiting for China and India to blink, and go ahead and impose mandatory emissions caps. China and India should do the same.


There is a new study out on the rate of ice loss in the Antarctic, relying on far more precise and comprehensive data than has been previously available. Not only is the ice mass shrinking, the rate of ice loss has increased by a whopping 75% over 10 years (from 1996-2006). Lead author Eric Rignot is quoted in the Globe & Mail: “I see [global warming] as the main driver for the change in ice mass. And this means that we are not in a natural cycle, but in something that is related to global warming or global climate change, whichever you want to call it.” The G&M story is at: [space inserted]wicesheet13/BNStory/National/home

The original paper is being published in a new journal in the Nature group, Nature Geoscience, here: But of course the paper itself is firewalled.

This study is particularly important because the 4th IPCC scenarios reckoned in the Greenland ice loss, but when they went to press there was no clear picture of what was happening at the other pole. Apparently the impact on sea level rise of what Rignot et al have found will be as significant as what’s happening in Greenland.

Fern Mackenzie

Not sure what to make of the new study. Other current data shows the Antarctic to be over 1,000,000 square kms above average for ice extant.

Secondly, there is also a new article published stating that the melting in Greenland is less now then it was in the 1920’s and 1930’s.

The new study is talking about a long-term trend, noting in particular that the rate of total ice mass loss over the last decade has accelerated to 75% faster than 1996. The current statistic you cite for above-average ice extent is seasonal variation of sea ice referring to ice formed this winter, I believe (is it not?), not long-term ice sheet mass data. As for the new study at, it refers to surface melting. As I understand it, the greatest loss of ice mass in the Greenland sheet occurs at the leading edge, where the ice is being dumped into the sea at a much higher rate than in the past. Surface melt contributes to the rate of flow of the glaciers, but is not the principle mechanism for loss of mass. (I’m no expert – if someone can confirm this I’d be grateful)

Fern Mackenzie

You are right, watching too. My guess is were watching ‘weather’ here. Weather driven by ‘La Nina’ presenting us a steadily growing worldwide effect.
Maybe 2008 will not be extremely hot. But underlying warming might very well go right on, spreading warmth to deeper ocean layers. The pack ice is just superficial. We may better be watching Larsen C. A new El Nino may trigger new temperature records in 2009. But don’t expect too much recovery of arctic pack ice in 2008. It’s bloody thin.

How about the “pingo-like features” on the Beaufort Sea shelf? The ones giving off bubbles of methane gas?

This paper from :
Target practice: Where should we aim to avoid dangerous climate change?
didn’t get a lot of play in the media (at least as far as I saw) when issued, but it does a good job of laying out the dynamics of where we are w.r.t. to “dangerous” change, and what a CO2eq ppm target should look like.

My guess as to the reason for its sparse coverage? They conclude that the target CO2eq ppm that is significantly below today’s level of ~ 382 ppm. AND, they published this slightly before both Bill McKibben and James Hansen recently made similar calls and created a minor cyclone in the blogosphere: see here for example:

This, of course, is far from the first time that we have been apprised of this. And even Hansen and McKibben clearly understand that we are certain to overshoot today’s numbers even if we do eventually get on our way to a lower number…

However, I still think large parts of the public - and political leaders - seem to struggle with the difference between “stock” and “flow” issues w.r.t. atmospheric concentrations… For instance, I think that the whole framing of (pick a number) “80% reductions in CO2 emissions by 2050” lulls people into a sense that “yeah, that’s a big cut, but ‘they’ (i.e. the future) will figure it out”… The problem with that is the PATH that we take to reductions is equally (or more) important to the final levels… e.g. if we were to keep emissions where they are today for the next 35 years and then abruptly cut by 80%, it would be “too little, too late” because the issue is a “stock” issue not a “flow” issue… I know that it patently obvious to anyone educated in the field, but sadly I think the reality is that this simple confusion continues to be a a major stumbling block to getting urgent action…

By the way, the further implication of a CO2eq ppm target of lower than today’s number is that, in effect, it requires “negative” CO2 emissions - another reason the concept is so daunting and almost anathema to present day economies… Inconveniently, “the climate” doesn’t give a rat’s a** if it is “daunting” or “anathema”… do…