Posted by: David Hone

How important is the two degree target?

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In a speech given at Dartmouth College at the beginning of this month, US Lead Climate Negotiator Todd Stern caused some consternation in the media by opening up the subject of the global two degree Celsius target. Bylines such as “US Abandons 2° Target” appeared soon after, to the extent that a further statement was made two days later by Todd Stern to say;

 “The U.S. continues to support this goal. We have not changed our policy.”

Reading the speech more closely, Stern had not dismissed the target at all nor questioned the necessity of making substantial reductions in global emissions. Rather, he had outlined a negotiating strategy which might bring nations to the table and actually get them to agree on something, rather than the status quo situation which has so far resulted in little progress.

 For many countries, the core assumption about how to address climate change is that you negotiate a treaty with binding emission targets stringent enough to meet a stipulated global goal – namely, holding the increase in global average temperature to less than 2° centigrade above pre-industrial levels – and that treaty in turn drives national action. This is a kind of unified field theory of solving climate change – get the treaty right; the treaty dictates national action; and the problem gets solved. This is entirely logical. It makes perfect sense on paper. The trouble is it ignores the classic lesson that politics – including international politics – is the art of the possible. . . .

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This kind of flexible, evolving legal agreement cannot guarantee that we meet a 2 degree goal, but insisting on a structure that would guarantee such a goal will only lead to deadlock. It is more important to start now with a regime that can get us going in the right direction and that is built in a way maximally conducive to raising ambition, spurring innovation, and building political will.

The 2°C target has been around for a while, but has no particular scientific basis. Rather, it represents an integrated assessment based on many inputs. From what I have been able to find, it appears to be the point at which various systems may see a step change in their response to rising temperatures. This includes the collapse of some major ice shelves, changes in major ocean current circulation, the demise of some marine ecosystems, extensive coral bleaching and so on. Much of this is summarized in an output document from a 2005 conference, Avoiding Dangerous Climate Change, convened by the British Government prior to their hosting of the G8. Although the EU had proposed a 2°C target well before 2005, it was at this conference and the following G8 meeting where it really took hold. Finally, at the UNFCCC COP in Cancun it was agreed as a formal goal, given that the objective of the Convention is to “avoid dangerous anthropogenic interference with the climate system”.

But the 2°C objective is just the beginning  of a long chain which must ultimately stretch down to the allowable emissions of a given power plant or the need to store a tonne of CO2 in a subsurface reservoir. This chain is riddled with uncertainty which almost never gets a mention. For example, many now link the 2°C objective with atmospheric stabilization of CO2 at a level of 450 ppm and in previous postings I have talked about 2°C equating to an atmospheric stock of one trillion tonnes of carbon. But these are levels that are associated with something around a 50% probability that global temperatures will plateau below a 2°C rise. In trillion tonne terms, based on a “business as usual” scenario, we will cross that point in about mid-2043. Shifting the bar such that we have a better than 75% chance of limiting the temperature rise to 2°C moves the crossover point back 15 years, to early 2028.

There is also no guarantee that we can collectively limit the temperature rise to below 2°C. Even if emissions stopped today, the range of possible outcomes from a 400 ppm CO2 level includes 2°C, albeit at quite a low probability. This is because the atmosphere is not in a state of heat equilibrium and will continue to warm at current levels of CO2.  As such, determining a target atmospheric CO2 concentration becomes difficult. 450 ppm is convenient in that it is above current levels, was feasible (at a stretch) when first raised and coincided with a 50% chance of limiting the temperature to 2°C. More recently James Hansen of GISS / NASA has argued for a target of 350 ppm, in that this would restore the current heat imbalance in the system and therefore stop the temperature rising. The problem with this goal is that we have already passed it and nobody really likes setting a target which can’t be met.

Further to the problem of determining a desired plateau for atmospheric CO2, comes the even more difficult task of translating this into a physical limit on global emissions. The task of halving emissions by 2050 is often discussed, but little mention is made of the fact that after 2050 the trajectory must head pretty rapidly to zero. Even the “half by 2050” goal has been obscured by a forgotten baseline year. For some it is 1990, others it is 2000 / 2005 or even just half compared to now. These are all very different. The original baseline when the “half” was first discussed was 1990, which for energy related emissions translates to a goal of 10 GT per annum – China today is at about 8 GT.

As already noted, CO2 acts like a “stock pollutant” in that it collects in the atmosphere. The best approach for this is to find a mechanism for limiting the cumulative CO2 emitted, in other words never emitting that trillionth tonne of carbon.

Framing the problem in this way then perhaps makes us think differently about the comments made by Todd Stern. Trying to carve up the space left in the atmosphere between 190+ nations may be a diplomatic stretch too far, so we should at least move with haste towards what we can do now. In the interim, as actions start to take root and countries realize that limiting emissions isn’t the end of life, the universe and everything, the door then opens to a more comprehensive approach. This would be an “evolving legal agreement” .

Such an approach isn’t the ideal, but given that “immediate global agreement” has very little chance of happening, it would appear to be the prudent way forward, but with the our sights still set on the 2°C goal.

Image: Melting Earth via Shutterstock

Authored by:

David Hone

David Hone serves as the Chief Climate Change Advisor for Royal Dutch Shell. He combines his work with his responsibilities as a board member and Chairman of the International Emissions Trading Association (IETA). Additionally, he works closely with the World Business Council for Sustainable Development and has been a lead contributor to many of its recent energy and climate change ...

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August 27, 2012

the earthling says:

Gaby Petron didn't set out to challenge industry and government assumptions about how much pollution comes from natural gas drilling. She was just doing what she always does as an air pollution data sleuth for the National Oceanic and Atmospheric Administration. "I look for a story in the data," says Petron. "You give me a data set, I will study it back and forth and left and right for weeks, and I will find something to tell about it." Petron saw high levels of methane in readings from a NOAA observation tower north of Denver. And through painstaking, on-the-ground detective work, she tied that pollution to the sprawling  gas fields in northeastern Colorado.

The story she stumbled into suggests that government may be far underestimating air pollution from natural gas production. Her measurements, which were published in the Journal of Geophysical Research, suggest that methane, a potent greenhouse gas, is leaking at at least twice the rate reported by the industry. Methane is very effective at trapping heat in the atmosphere. And already, natural gas production is the biggest manmade U.S. source of methane.Petron says even the lowest range of her estimate was higher than the leak rate industry and regulators were reporting. "Really, what our story is telling in our paper is the leak rate is twice what the industry thinks it is," she says.


Petron's work also suggests that the industry is underestimating its releases of other chemicals, including benzene, which, if present at high enough levels, can cause cancer. The industry reports negligible benzene emissions. But her calculations show it is likely the region's largest source of benzene.

source cited..


Position on Global Warming

167 countries responsible for more than 87 percent of the world's carbon emissions have signed on to the Copenhagen Accord, endorsing the two-degree target. Only a few dozen countries have rejected it, including Kuwait, Nicaragua and Venezuela. Even the United Arab Emirates, which makes most of its money exporting oil and gas, signed on. The official position of planet Earth at the moment is that we can't raise the temperature more than two degrees Celsius – it's become the bottommost of bottom lines. Two degrees. Scientists estimate that humans can pour roughly 565 more gigatons of carbon dioxide into the atmosphere by mid-century and still have some reasonable hope of staying below two degrees. We have five times as much oil and coal and gas on the books as climate scientists think is safe to burn. We'd have to keep 80 percent of those reserves locked away underground to avoid that fate. Before we knew those numbers, our fate had been likely. Now, barring some massive intervention, it seems certain.Yes, this coal and gas and oil is still technically in the soil. But it's already economically above-ground – it's figured into share prices, companies are borrowing money against it, nations are basing their budgets on the presumed returns from their patrimony. It explains why the big fossil-fuel companies have fought so hard to prevent the regulation of carbon dioxide – those reserves are their primary asset, the holding that gives their companies their value. It's why they've worked so hard these past years to figure out how to unlock the oil in Canada's tar sands, or how to drill miles beneath the sea, or how to frack the Appalachians.


 We know how much we can burn, and we know who's planning to burn more. Climate change operates on a geological scale and time frame, but it's not an impersonal force of nature; the more carefully you do the math, the more thoroughly you realize that this is, at bottom, a moral issue. 


source cited;




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August 18, 2012

S. Loving says:

I totally don't get itl  Truly.  I don't get it.  When Pearl Harbor was bombed we didn't talk about the cost, the feasibility.  We saw the risk to our kids and grandkids and set about to win, to WIN the war.  I don't recall talk of accommodating Hitler, making a deal with him, giving him Part of the US, part of our children's income....  I don't recall that.

But in unilaterally agreeing to 2 degrees C that is exactly what we've done.  Sure, we can imagine that it will only destroy the Bangladeshis, Athabascans, Indigenous Alaskans, Maldivians....  But, you know what?  They are the canaries in the coal mine called earth.  We let them die, and 2 degrees C is a death sentence, and out grandkids are next.

Huh?  I don't get it.

Over my dead body.  Death Fast in front of the Canadian Embassy - Day 6.

Google 'start loving.'  Google 'Tracking Plan B.'

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August 17, 2012

Jim Baird says:

Another perspective.

A recent Congressional Reaserch Service study found the total procurement costs for all US wars was just just less than $7 trillion.

Presumably these trillions were and are being spent for the expressed purpose of preserving a way of life and standard of living that are at mortal risk due to climate change.

The insurance company Allianz suggest $28 trillion worth of coastal infrastructure is at risk due to sea level rise alone by 2050.

Debate instead of action is unconscionable.

Clearly our priorities are skewed.


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August 18, 2012

Robert Bernal says:

We should spend at least $1 trillion "just" for the machinery to mass produce (the best RE storage) batteries and solar panels for pennies on the dollar. I'm sure that resulting installations would more than pay back the expendature in the long run.

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August 18, 2012

Jim Baird says:

All the energy we need is already stored in the ocean, causing it to expand, melt the icecaps and damage the life that lives there.

We need to get that heat out and prevent more from being placed there.

OTEC gets it out and replaces the CO2 emissions that are causing the build up.

No other energy source serves both purposes.

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August 17, 2012

Adam James says:

I agree that 2C isn't useful when used to create a global budget and then a top down allowance for emissions from various countries- but I do think it is useful to conceptualize the kind of emissions path which is sustainable vs. our BAU path. We can use that mark to gauge our progress, even if our means of hitting 2C isn't a top down treaty. The US notion (advocated by Stern) about flexible national goals- particularly those which harness public private partnerships- will probably do more to get us where we need to go than the stop/start negotiations for global mandates.

That said, I fully support continuing the UNFCCC process in the hopes of getting binding emissions targets- as that would be more effective if it could come together.

I also wrote on the 2C controversy here:


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