“It’s the most dire prediction yet”!!!

Guest post by David Middleton

Featured image borrowed from here.

In even the bleakest climate change scenarios for the end of this century, science has offered hope that global warming would eventually slow down. But a new study published Monday snuffs out such hope, projecting temperatures that rise lockstep with carbon emissions until the last drops of oil and lumps of coal are used up. Global temperatures will increase on average by 8 degrees Celsius (14.4 degrees F) over preindustrial levels by 2300 if all of Earth’s fossil fuel resources are burned, adding five trillion metric tons of carbon to the atmosphere, according to the research by Canadian scientists published in Nature Climate Change. In the Arctic, average temperatures would rise by 17 degrees C (30.6 degrees F). Those conclusions are several degrees warmer than previous studies have projected. If these temperatures do become reality, greenhouse gases would transform Earth into a place where food is scarce, parts of the world are uninhabitable for humans, and many species of animals and plants are wiped out, experts say. “It would be as unrecognizable to us as a fully glaciated world,” says Myles Allen, head of a climate dynamics group at the University of Oxford in the United Kingdom. Allen was not involved in the new study, but his research has focused on carbon’s cumulative impacts on climate. Noting that it took less warming, 6 degrees C (10.8 degrees F), to lift the world out of the Ice Age, Allen said, “That’s the profundity of the change we’re talking about.” […] NatGeo

What croc of schist!

First off, we haven’t been lifted “out of the Ice Age.” Earth has been in an ice age since the Oligocene. We are fortunate enough to be living in an interglacial stage of an ice age.

The current atmospheric concentration of carbon dioxide doesn’t even break out of the Cenozoic noise level…

This latest bit of nonsense from NatGeo is based on Katarzyna et al., 2016. Here’s the abstract…

NATURE CLIMATE CHANGE | LETTER The climate response to five trillion tonnes of carbon Katarzyna B. Tokarska, Nathan P. Gillett, Andrew J. Weaver, Vivek K. Arora & Michael Eby Nature Climate Change (2016) doi:10.1038/nclimate3036 Received 29 July 2015 Accepted 21 April 2016 Published online 23 May 2016

Concrete actions to curtail greenhouse gas emissions have so far been limited on a global scale1, and therefore the ultimate magnitude of climate change in the absence of further mitigation is an important consideration for climate policy2. Estimates of fossil fuel reserves and resources are highly uncertain, and the amount used under a business-as-usual scenario would depend on prevailing economic and technological conditions. In the absence of global mitigation actions, five trillion tonnes of carbon (5 EgC), corresponding to the lower end of the range of estimates of the total fossil fuel resource3, is often cited as an estimate of total cumulative emissions4, 5, 6. An approximately linear relationship between global warming and cumulative CO 2 emissions is known to hold up to 2 EgC emissions on decadal to centennial timescales7, 8, 9, 10, 11; however, in some simple climate models the predicted warming at higher cumulative emissions is less than that predicted by such a linear relationship8. Here, using simulations12 from four comprehensive Earth system models13, we demonstrate that CO 2 -attributable warming continues to increase approximately linearly up to 5 EgC emissions. These models simulate, in response to 5 EgC of CO 2 emissions, global mean warming of 6.4–9.5 °C, mean Arctic warming of 14.7–19.5 °C, and mean regional precipitation increases by more than a factor of four. These results indicate that the unregulated exploitation of the fossil fuel resource could ultimately result in considerably more profound climate changes than previously suggested.

Nature made the full paper available for reading here

Here’s a quote from the first paragraph of the main body of the paper…

We analyze prescribed-concentration simulations from… (CMIP5) driven by the Representative Concentration Pathway 8.5 Extension scenario (RCP8.5-Ext)…

In summary:

Make a WAG as to the total fossil fuel resource potential (presumably the authors know the difference between reserves and resources). Assume mankind will burn all of it over the next 284 years. Apply RCP 8.5 “The stuff nightmares are made from”. Issue “most dire prediction yet.”

I will give them “credit” for not using the phrase “business as usual.” However, the following quote from the abstract is just a wordy version of “business as usual.”

In the absence of global mitigation actions, five trillion tonnes of carbon (5 EgC), corresponding to the lower end of the range of estimates of the total fossil fuel resource, is often cited as an estimate of total cumulative emissions.

RCP 8.5 is bad science fiction…

Based on a real world “business as usual” emissions scenario, with natural gas displacing oil at its current pace and no carbon tax, I come up with a CO2 right about inline with RCP 6.0, “a mitigation scenario, meaning it includes explicit steps to combat greenhouse gas emissions (in this case, through a carbon tax)“.

Then I took my real world “business as usual” relative concentration pathway and applied three reasonable climate sensitivities to it: 0.5, 1.5 and 2.5 °C per doubling of atmospheric CO2, starting at 280 ppmv (TCR 0.5, TCR 1.5 and TCR 2.5). HadCRUT4, referenced to 1850-1879 is clearly tracking very close to TCR 1.5…

Since it is generally assumed that at least half of the warming since 1850 was natural, the actual climate sensitivity would have to be significantly lower than 1.5 °C per doubling. Therefore, RCP 8.5 should never be described as “business as usual,” “expected” or a “baseline case.” Since its assumptions are mind mindbogglingly unrealistic, it shouldn’t be used in any serious publication. It is bad science fiction. LINK

Otherwise, Katarzyna et al., 2016 is “rock solid”science. NatGeo, on the other hand, is about as scientific as the SyFy channel.

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