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Assessing the Impact of Global Peak Oil on the Climate

Atmospheric carbon dioxide changes over time for the study’s five fossil fuel scenarios: business-as-usual (a), coal phase-out (b) and oil use and supply (c-e). Click to enlarge. Credit: NASA/Kharecha and Hansen

A new paper by Pushker Kharecha and James Hansen at the NASA Goddard Institute for Space Studies and Columbia University Earth Institute shows that if proven conventional oil and gas reserves do not greatly exceed estimates of the Energy Information Administration—i.e., if conventional production peaks during the next few decades—it will be feasible to keep atmospheric CO2 from exceeding about 450 ppm by 2100, provided that emissions from coal, unconventional fossil fuels, and land use are constrained. Their paper was published 5 August in the American Geophysical Union’s journal Global Biogeochemical Cycles.

Although a limit of 450 ppm CO2 is one of the more ambitious emissions targets proposed by governments and corporations, the Intergovernmental Panel on Climate Change (IPCC) estimates that even at that limit, there is a 20% likelihood that global temperatures will increase by 3.5º C or more. In April, Hansen called for a global target of 350 ppm. (Earlier post.)

This is the first paper in the scientific literature that explicitly melds the two vital issues of global peak oil production and human-induced climate change. We’re illustrating the types of action needed to get to target carbon dioxide levels.

—Pushker Kharecha

To better understand the possible trajectory of future carbon dioxide concentrations, Kharecha and Hansen devised five carbon dioxide emissions scenarios that span the years 1850-2100. Each scenario reflects a different estimate for the global production peak of fossil fuels, the timing of which depends on reserve size, recoverability and technology.

Even if we assume high-end estimates and unconstrained emissions from conventional oil and gas, we find that these fuels alone are not abundant enough to take carbon dioxide above 450 parts per million.

—Pushker Kharecha

The first scenario estimates carbon dioxide levels if emissions from fossil fuels are unconstrained and follow along business as usual, growing by two percent annually until half of each reservoir has been recovered, after which emissions begin to decline by two percent annually.

The second scenario considers a situation in which emissions from coal are reduced first by developed countries starting in 2013 and then by developing countries a decade later, leading to a global phase out by 2050 of the emissions from burning coal that reach the atmosphere. The reduction of emissions to the atmosphere in this case can come from reducing coal consumption or from capturing and sequestering the carbon dioxide before it reaches the atmosphere.

The remaining three scenarios include the above-mentioned phase out of coal, but consider different scenarios for oil use and supply. One case considers a delay in the oil peak by about 21 years to 2037. Another considers the implications of fewer-than-expected additions to proven reserves due to overestimated reserves, or the addition of a price on emissions that makes the fuel too expensive to extract. The final scenario looks at emissions from oil fields that peak at different times, extending the peak into a plateau that lasts from 2020-2040.

Next, the team used a simplified mathematical model, called the Bern carbon cycle model, to convert carbon dioxide emissions from each scenario into estimates of future carbon dioxide concentrations in the atmosphere.

The unconstrained business as usual scenario resulted in a level of atmospheric carbon dioxide that more than doubled the preindustrial level and from about 2035 onward levels exceed the 450 parts per million threshold of this study. Even when low-end estimates of reserves were assumed, the threshold was exceeded from about 2050 onwards.

However, the other four scenarios resulted in carbon dioxide levels that peaked in various years but all fell below the prescribed cap of 450 parts per million by about 2080 at the latest, with levels in two of the scenarios always staying below the threshold.

The researchers suggest that the results illustrated by each scenario have clear implications for reducing carbon dioxide emissions from coal, as well as unconventional fuels such as methane hydrates and tar sands, all of which contain much more fossil carbon than conventional oil and gas.

It is also important to “stretch” conventional oil reserves via energy conservation and efficiency, thus averting strong pressures to extract liquid fuels from coal or unconventional fossil fuels while clean technologies are being developed for the era “beyond fossil fuels&rduqo;. We argue that a rising price on carbon emissions is needed to discourage conversion of the vast fossil resources into usable reserves, and to keep CO2 beneath the 450 ppm ceiling.

—Kharecha and Hansen (2008)

Because coal is much more plentiful than oil and gas, reducing coal emissions is absolutely essential to avoid dangerous climate change brought about by atmospheric carbon dioxide concentration exceeding 450 parts per million. The most important mitigation strategy we recommend—a phase-out of carbon dioxide emissions from coal within the next few decades—is feasible using current or near-term technologies.

—Pushker Kharecha




WAKE UP !!!!!!!!!!!!!!!!

Global Peak Oil is not decades away.
Perhaps we are now at Peak Oil, and if not, maybe sooner than 2013.
But we do NOT have 10 years!!

Twilight in the desert.
Beyond Oil.

A Crude Awakening, The Oil Crash



Why do you think a lot of us read this site Jorge?!


If peak oil production is reached, there will be a lot of pressure to tap the non-traditional energy sources. With these non-traditional sources being less efficient, I could argue that the emission could become worse.

This could be a fight that will last 100 years, since there are no easy silver bullets, and there are a number of early "gotcha" tipping points. For example, I don't know how we can avoid losing the ice cap, and the perma-frosts.

Albert G

I'm excited to see the shrieks of Global Cooling again. In the 1970's "scientists" actually proposed setting off nuclear bombs to help melt the Acttic ice. Or cover Arctic ice with soot to help it melt. Global Cooling was going to KILL US ALL!!!

It's great that the shrieks have turned to Global Warming. Even though the Earth has been in a cooling trend for the past decade.

Anything to get research money and control people's lives...


Oh Albert! Please site your sources about global cooling.


And Albert - Limbaugh and Hannity aren't credible sources for citation.

Don't beleive the hype your hear from political zealots - either on the left or on the right. Look at peer revieved science and then make your judgements.

And there's a lot less money in research than there is in the oil lobby, so use some strong economics to determine who is more motivated to use junk science.

And thanks for the laugh!


So the likes of Albert would have coal to liquids which will only make the matter a lot worse.

Hard to beleive there are real people like this.

It would seem that the Americans and other willings have an angle on this - start another war this time with China?
Solve the balance of trade and divert he publics attention in one.
"Crisis?" - "not now!"
"Can't you see we have a war on our hands?"
Thats a politician job it would seem.
Just maybe they can wait till after the (US) election.


Every vehicle in the US could be electric tommorrow and it wouldn't do any good at all if China and India don't follow suit.

Oh, in ten years, we will have 8 Billion humans on planet earth. I don't think the Ice Caps have much of a chance.



There may be a scramble to use coal for CTL and some plants will be built. While the few individual plants may be messy with high specific CO2 emission, they will hardly dent the decline of even the Cantarell field in Mexico.

The human ressources to build these plants do not exist. I'm one of them and I'm plenty busy working on something else (Carbon capture from pulverized coal fired power plants)

And with new cars coming out, such as the Golf Mk VI Bluemotion with 68 mpg consumption, there will be enough liquid fuels to get to work.

PHEVs can futher stretch liquid fuels, fueled by renewable energy, or even clean coal or nulear (Bush: nucular ;-)). Thus, I'm not too worried about Peak Oil.

Regarding global warming and melting ice caps, I think our conventional thinking is flawed. Since the invention of photography it has been some 140 years, a relatively short period for natural climate changes. For much of that short period, the climate seemed constant, but in reality it is always changing. Througout climate history, even within the last 10,000 years there have been several periods without polar ice, a white-tipped Kilimanjaro and gleischers in the Pyrenees. This ice is not "supposed to be there", just because it happened to be so AD1870-1980.

I wish I could point to some great sources. The best source I have was an interview with the leading Danish glaciologist (responsible for the ice core measurements on Greenland) on Danish TV. With his 'Greenpeace zealot demeanour he critisized the notion that melting polar ice is evidence of anthropogenic global warming and showed that throughout human history in Europe, people have thrived in warm periods and suffered during cold spells. Quite thought provoking, I think. I can also recommend Michael Crichtons book 'State of Fear' from 2004.

I am not saying we should dismiss the fear of global warming altogether, but perhaps strive for a balanced view. Still, I think we should attempt not to make too big a mess of our environment and I do believe greater use of renewable energy will be a good idea, even economically. Especially in the long run, but I guess it is really 'free' for me to state that :-)

Coming back to Peak Oil. I see evidence that global market forces are handling this problem, contrary to what I thought was possible just a couple of years ago. I does not take that many commuters to switch from Hummers to Golf Bluemotion (not available in the US, I know) to show on the statistics of fuel usage. And remember, the new economical cars will tend to be used the most, even if the Hummer is still sitting in the garage. In other words, 'Don't panic'


Everybody knows that Peak Conventional Oil will be here within two or three decades; that Peak Non-Conventional Oil will also be here by 2100 or so; that peak Coal may also be here within a century or so. In reality, that is all very good news for humanity's survival. The soonest the better.

The best news is that Peak Solar Power may not come for another 5+ billion years (if we are still around to capture and use it). The sun can provide all the clean energy we require many times over and the technologies to capture, store and use it are here already. Of course, we will do it more efficiently within a decade or two, but since it is so plentiful, even at 10% capture efficiency, we have more than enough.

Other clean electrical energy sources such as Hydro, Geothermal, Wind, Biomass and Nuclear can supply, in many areas, a high percentage of the requirement.

We went from being pedestrians to animal back riders, to steam train riders, to current ICE machines users without major adaptation problems.

We will certainly adapt to electrification of most, if not all, of our industries, commercial and domestic HVACs and most of our transportation means during the current century.

The only thing to worry about is the slow transistion pace. Instead of taking one full century, it could be done in half a century or before the Earth is too polluted.

We should promote the change and not buck it.

richard schumacher

Thomas, do you really think it's physically possible to handle and permanently store more than a cubic mile of liquid CO2 every year? Even if it is, how can it be economical? The DOE's lowest estimate of the cost for CCS is $35 per tonne of carbon. At that cost coal is more expensive than nuclear and wind, and perhaps thermal Solar.

Chrichton was a medical doctor and science fiction writer, not a scientist, so his opinions on global warming are insignificant.


Lots of people talk about peak oil from the supply side. No one ever talks about "peak demand."

US petroleum demand appears to have peaked in Nov 2007... There are both structural and economic reasons to believe these demand reductions are not short term but will persist for the next couple of years, at least. Beyond then there is such vast improvement on the horizon for US consumer vehicle choices that seeing oil demand greater than our old peak of around 20.8mbpd is difficult.


"Chrichton was a medical doctor and science fiction writer, not a scientist, so his opinions on global warming are insignificant.

Al Gore is not a scientist either, Bachelor of Arts in government, is his opinions on global warming insignificant?


Some people still seem to think the US is the center of the universe, and everyone else is in the dark ages.

China is producing BEV's, and they, along with India have to pay for the same declining supply of oil as we do (although they can do it with our money). EU has the Golf Bluemotion and we don't. In other words, we are all in the same boat, everyone will be bailing.



yes, they are.

@ Joseph

"Al Gore is not a scientist either, Bachelor of Arts in government, is his opinions on global warming insignificant?"

Agreed, Gore's point of view isn't what matters. All that matters is peer reviewied science, which very strongly supports accelerated global warming caused by greenhouse gasses. Gore's a chump, right sometimes, wrong other times and always annoying.

But that doesn't mean his concern is misplaced.


post above is mine


I agree with many commenters above. These guys made ridiculous assumptions in these graphs. Peak oil is now, not in 21 years. And most fossil reserves will stay in the ground because, by then, renewables will be cheaper. Simple economics.

I am, however, very happy to see the Nobel crowd finally admitting that CO2 emission will decrease by themselves, with or without Kyoto. So far, the only scenario considered by the IPCC was the first graph which assumes we will never run out of oil-coal-gas. What will they admit next: that Bush was right?

Reality Czech

There is an enormous amount of un-mineable coal which can nevertheless be used by methods such as in-situ gasification. The cheapest way to use the resulting syngas is to make methane or methanol from it, and dump the CO2. This multiplies the CO2 output for the same amount of useful energy.

Regardless of what happens to oil, CO2 emissions are not guaranteed to decrease.


Sorry but CO2 will not decrease by themselves because they put in the caveat "... provided that emissions from coal, unconventional fossil fuels, and land use are constrained."

So there are policies to enact and structural changes to the way society does things like developement, transportation, and energy production even with the constraints of peak oil, which basically makes thing more difficult with the installed inefficient infrastructure and capital.

Actually the IPCC does multiple scenario modeling as well. You just never hear of it because someone is always trying to present their side of it.


"Chrichton was a medical doctor and science fiction writer, not a scientist, so his opinions on global warming are insignificant."

Algore was a divinity school dropout and failed prexy candidate.


Even in the elevated CO2 environment of 450ppm we will see beneficial effects on important crops such as sugarcane. In a recent study sugarcane grown under elevated CO2 (-720ppm) was observed to demonstrate:

"increase of about 30% in photosynthesis and 17% in height, and accumulated 40% more biomass in comparison with the plants grown at ambient [CO2]."

Reminding us that not all CO2 scenarios are filled with doom - it is essential to plant life. And CO2 does not drive temperature, it follows it.


CO2 as a breakdown product of methane is one explanation offered for high rates of CO2 following temperature rise.
The levels of CO2 have been interpreted as low - 180 ppm when photosynthesis is high. Plants reduce CO2 to low levels when there is a large organic carbon store.
When that store crashes (for whatever reason - fires from high O low co2/ nitrogen?) there is a large release of CO2 methane.
The exact mechanism for any previous event may not be known and there are likely different circumstances surrounding past climate shifts.
But we do understand how these interactions work to shift climate and how carbon sequestration is the main mechanism for climate stabilisation.

the US could stop buring all fuels and go back to horses and buggies and China plus India will double our reduction in less than a decade all the while pointing and laughing at the fools who trashed there standards of living for the marxist cult of global warming. wake up people if GW is real then we must go to WAR with China and India to FORCE them to cut emmissions to levels that do not exceed some made up level.

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