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Scientists Warn That Warming ‘Will be Hard to Reverse’

By Tim Radford, Climate News Network

LONDON – A Swiss-American team of scientists has looked far into the future and calculated that the present lukewarm plans to limit climate change may involve too little action, applied too late.

The simulation shows a serious fading in the polar oceans’ ability to remove surplus heat.
Credit: Antarktika, Wikimedia Commons via Climate News Network

Thomas Frölicher of ETH-Zurich and colleagues from Princeton report in Nature Climate Change that they tried to model the long-term planetary adjustment after carbon dioxide emissions from fossil fuel burning stopped altogether.

They simulated a planet in which greenhouse gas emissions continued to rise, until concentrations in the atmosphere had reached four times the pre-Industrial levels, and a total of 1,800 billion tons had been released into the atmosphere. And then the emissions stopped.

The consequences were unexpected. The carbon dioxide in the atmosphere would indeed gradually be absorbed by forests, crops, algae and other natural CO2 devourers; it would be incorporated into the calcium shells and corals and skeletons in the ocean and then slowly be tucked away as rock.

But after an initial period in which temperatures started to drop, something else happened. The simulated planet started to warm again, and go on warming for another 400 years or more.

Oceans’ influence dims

That is because although what scientists call “radiative forcing” – CO2 traps infra-red radiation and keeps the Earth’s temperature up – would begin to ease, the polar oceans that play such a powerful role in the climate machine would become less efficient at removing the surplus heat.

The logic of all this rests on the reasoning that life on Earth for the last 10,000 years has continued comfortably with a particular ratio of CO2 to other gases in the atmosphere. To increase carbon levels significantly – and this has already begun to happen – would therefore disturb this comfortable equilibrium, and then trigger a very long period of uncertainty.

Frölicher and colleagues found that 40 percent of the extra carbon in the atmosphere would have been soaked up within 20 years, and 80 percent within 1,000 years. This would of course affect temperatures.

First, as the carbon dioxide levels reached a maximum, the world would warm sharply and then, after 15 or 20 years, start to cool. The cooling could continue for a century.

Research suggests that even if carbon dioxide emissions came to a sudden halt, the carbon dioxide already in Earth's atmosphere could continue to warm our planet for hundreds of years.
Credit: Eric Galbraith, McGill University

Little time

But in the simulation, after the initial 100-year cooling-off period the Earth started to warm again. It went on warming for 400 years, by 0.37°C. This doesn’t sound much – but the Earth has already warmed by 0.85°C over pre-Industrial averages.

The world’s governments have collectively agreed that it would be good if the rise in average global temperatures could be halted at 2°C, and they have accepted in principle – serious concerted action has yet to be agreed – that with 500 billion tons of CO2 already released into the atmosphere, the safe limit should be 1,000 billion. But this now looks less plausible.

“If our results are correct, the total carbon emissions required to stay below 2°C of warming would have to be three quarters of previous estimates, only 750 billion tons of carbon,” said Frölicher. “Thus, limiting the warming to 2°C would require keeping future cumulative carbon emissions below 250 billion tons, only half of the already emitted amount of 500 billion tons.”

The research is a simulation, and the real lesson is probably that researchers still have a lot of work to do to understand the subtle relationships between atmosphere and ocean. But it suggests that the climate problem is more urgent than anyone may have realized.

“This is illustrative of how difficult it may be to reverse climate change – we stop the emissions but we still get an increase in the global mean temperature,” says Frölicher.

Tim Radford is a reporter for Climate News Network. Climate News Network is a news service led by four veteran British environmental reporters and broadcasters. It delivers news and commentary about climate change for free to media outlets worldwide.


By Eric Peterson (Front Royal, VA 22630)
on December 1st, 2013

“Frölicher and his co-authors showed that the change in ocean heat uptake in the polar regions has a larger effect on global mean temperature than a change in low-latitude oceans, a mechanism known as “ocean-heat uptake efficacy.”.”

The main problem with this conclusion is that the climate models being used cannot model weather which is the key factor in ocean heat uptake.  A small difference in clouds and weather makes a huge difference in heat uptake over a season.  That is obvious from looking at the difference between 2012 with record low Arctic sea ice and the 2013 rebound.  The predictions for the Arctic in 2013 were incorrect.  Here are the predictions; and the actual was 5.1 million sq km.  Some of these predictions use the exact same climate models used for the long term predictions that are the basis for the claim in this article.

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By Philip Haddad (Alvin, TX 77511)
on December 1st, 2013

Global warming is caused by heat emissions from fossil fuels and from nuclear energy. They add four times as much heat as can be accounted for by the actual measured rise in atmospheric temperature. The models based on CO2 totally ignore this major contribution and must be considered useless as a predictor of future events. Yes, it will be hard to reverse the effects of global warming, not because CO2 is too high, but because it is difficult to replace fossil fuel and nuclear energy with renewable sources such as solar, wind, hydroelectric, geothermal, tidal, etc. When the heat sources are removed temperatures will come down, and photosynthesis will help by removing 5000 btus of solar energy for every pound of CO2 converted, that otherwise would become heat. The higher the CO2 the more efficient the conversion efficiency. The nice thing about this hypothesis is that anyone can confirm this for himself. The mass of the atmosphere is 1166x10E16 pounds with a specific heat of 0.24. The energy consumption in 2008 was 50x10E16 btus. Temperature could have risen by 0.17*F, but actual rise was ~0.04 *F. Carbon capture and storage,CCS, has been proposed as a possible solution but consider this: In order to lower the CO2 concentration by one part per million, 18,000,000,000,000, pounds would have to be removed. How much cost and energy wasted and for what benefit? The U.S. and China have agreed to study this proposal. I believe that the world leaders should ask the scientists who declared CO2 to be the cause, to reassess their findings and include heat emissions in their calculations or explain how this heat can leave without any noticeable effects,(including glacial melting). Express your concerns to your elected officials, (if you are fortunate enough to get a response).

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By Eric Peterson (Front Royal, VA 22630)
on December 2nd, 2013

Philip Haddad, here is a table with orders of magnitude of energy of various sources:  The world’s energy use is 10^20 Joules per year.  Compare that to the energy from the sun in one year: 20^24.  Even if all the energy mankind uses turns to heat rather than potential energy, then man’s heat production is still 1/100 of the sun’s striking energy.  1/3 of the sun is reflected away so that brings down the ratio a bit.  But still the heat from man’s energy sources is trivial.

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By dan_in_illinois
on December 2nd, 2013

It looks like the warming trend may already have been reversed:

The article is from the UK Daily Mail and describes the 29% increase that has occurred in the Arctic icecap since 2012, despite warnings from climate “experts” that the Arctic would be ice-free by 2013 due to AGW (the particular prediction cited was made on the BBC back in 2007).

If I were the “experts”, I would stop talking about warming and switch back to Climate Change.  With that one, you pretty much can’t be wrong, no matter what the climate does.

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By Frank Elliott (Richfield/Minnesota/55423)
on December 2nd, 2013

The fact that humans and our burning of carbon fuels is causing global warming and climate change is not a fact up for debate anymore.  Almost all refereed articles and conference papers firmly show that human additions of carbon dioxide to our atmosphere by gradually increasing amounts over about the last 150 years has reached the point where it is clearly causing climate warming and ocean warming.  Now what we need to do is to get on with is trying to mitigate this warming.  If we don’t, we won’t be around much more than a few hundred years as a species with a long term future.  It is not so important to argue the he total amount of warming, but how much our planet has been thrown out of an equilibrium state.  Even a very small additional quantity like much less than 1% of additional warming has been gradually added to destabilize our climate’s temperature equilibrium point. It’s that way here where our additional many billions of tons of greenhouse gases per year are tilting a long established equilibrium toward warming by just a small fraction of a degree gradually over time. The issue is the imbalance between how much heat the earth can both reflect and radiate out and how much heating there is year after year and century after century.  I also want to call attention to the fact that the issue is not the extent of very thin ice and wide variance from one year to another in this thin sea ice near arctic or arctic waters that melts and then reforms year after year.  The more important issue is the volume of ice overall in all locations.  That volume measurement has been dipping ever so gradually down as a trend and the trend is directly correlated to the ever rising level of carbon dioxide, methane and other greenhouse gases in the atmosphere.  This is my impression and the conclusions I have drawn after years and years of reading and being involved deeply in the research process as a science and engineering librarian with a deep background in science and statistics/mathematics.

Here’s my uncertainty about all of this based on my reading and thinking.  I believe we have not yet established how much the warming will be with accuracy nor precision.  We don’t understand the dynamics of climate, weather, and air/sea/land interactions well enough yet to know if this warming will be 1 or 2 degrees or perhaps as high as 5 degrees or more.  To me this uncertainty is very worrying, but I really believe that all countries need to reduce our use of carbon based fuels relatively rapidly very soon.  I’m doing my part by moving to smaller, much more fuel efficient vehicles and reducing our energy use as much as possible.  More and more of us need to also conserve and reduce our use of energy as much as we are able.  I wish we were all able to move this discussion into a more object and logical realm and take us much of our politics and preconceptions out of this very important issue for humankind’s future and the future of our rich natural ecosystems.

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By john harkness
on December 2nd, 2013

Eric, thanks for that very succinct answer to Philip. Nicely done.

I’m not sure I fully understand your point in your own first post here, though. Don’t you think there is a big difference in a one-year prediction of what your rightly call weather and a long term prediction of climate-driven consequences.

I certainly do think that the Arctic is likely to continue to react in ways that surprise and confuse just about everyone.

My question about this study is whether they have included carbon feedbacks.

I would just note that others have previously concluded that warming would remain or continue even with immediate cessation of GHG emissions:

    “climate models suggest that ocean warming will continue for at least a thousand years even if CO2 emissions were to completely stop”

And note the mid (dashed) line in the first graph at figure 3 in this piece:

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