A new study was published in the journal Nature Geoscience. It has been causing a bit of a stir – along with some real consternation – amongst the Climate Change crowd.
All the more so since the study was done by a group of well-known scientists who are not Global Warming Skeptics. Indeed, they have all been firmly entrenched within the Anthropogenic (man-made) Global Warming camp.
These are the actual scientists who have been responsible for determining and producing the United Nations’ Intergovernmental Panel on Climate Change (IPCC)’s Carbon Budget.
And they are finally admitting they were wrong…
The study is called Emission Budgets and Pathways Consistent with Limiting Warming to 1.5°. From the study:
The Paris Agreement has opened debate on whether limiting warming to 1.5 °C is compatible with current emission pledges and warming of about 0.9 °C from the mid-nineteenth century to the present decade. We show that limiting cumulative post-2015 CO2 emissions to about 200 GtC would limit post-2015 warming to less than 0.6 °C in 66% of Earth system model members of the CMIP5 ensemble with no mitigation of other climate drivers, increasing to 240 GtC with ambitious non-CO2 mitigation. We combine a simple climate–carbon-cycle model with estimated ranges for key climate system properties from the IPCC Fifth Assessment Report. Assuming emissions peak and decline to below current levels by 2030, and continue thereafter on a much steeper decline, which would be historically unprecedented but consistent with a standard ambitious mitigation scenario (RCP2.6), results in a likely range of peak warming of 1.2–2.0 °C above the mid-nineteenth century. If CO2 emissions are continuously adjusted over time to limit 2100 warming to 1.5 °C, with ambitious non-CO2mitigation, net future cumulative CO2 emissions are unlikely to prove less than 250 GtC and unlikely greater than 540 GtC.
If their conclusion presented in the opening of the study sounds a bit abstruse and esoteric, well, you’re not alone.
As the results are obvious to Climate Scientists, the authors would prefer not to lead with a headline that simply says, “We were wrong, the Climate Models have Been Running Overly Hot”.
But that’s exactly what their conclusions state.
According to the IPCC models, the world should be 1.3 °C above the mid-19th-Century temperature average. However, the most recent observations suggest the earth is actually about 0.9 °C above the mid-19th-Century temperature average.
These findings have enormous implications.
While 0.4 °C might not seem like that much, the difference in actual earth temperature versus projected is hugely significant.
“When you are talking about a budget of 1.5 degrees, then a 0.4 degree difference is a big deal”, said Professor Myles Allen, of Oxford University and one of the authors of the new study.
It also means the IPCC’s modeling of our “Carbon Budget” – and all the associated projections – are incorrect.
The IPCC models have been projecting that temperatures would exceed 1.5 °C by 2022. The last IPCC Assessment made exactly this prediction.
For this to occur, global temperatures would have to rise by 0.6 °C by 2022. This rise in temperature is – by the scientists own admission – virtually impossible.
Global average temperatures can increase as much as 0.25°C per decade. That means it should take over 20 years to go from 0.9°C today to 1.5°C. We emit about 40 billion tons CO2 per year, which gives us a budget of about 800 billion tons of CO2 if emissions remained constant.
That rough estimate of 800 billion tons of CO2, is much larger than the 250 billion tons CO2 suggested in the last IPCC report.
From a Washington Post article on the findings:
In 2013, the United Nations’ Intergovernmental Panel on Climate Change (IPCC) calculated that humanity could emit about 1,000 more gigatons, or billion tons, of carbon dioxide from 2011 onward if it wanted a good chance of limiting warming to 2 degrees C — launching the highly influential concept of the “carbon budget.”
The allowable emissions or budget for 1.5 degrees C would, naturally, be lower. One 2015 study found they were 200 billion to 400 billion tons. And we currently emit about 41 billion tons per year, so every three years, more than 100 billion tons are gone.
A recent study put the chance of limiting warming to 1.5 degrees C at 1 percent. Peters said that according to the prior paradigm, we basically would have used up the carbon budget for 1.5 degrees Celsius by the year 2022.
That’s what makes the new result so surprising: It finds that we have more than 700 billion tons left to emit to keep warming within 1.5 degrees Celsius, with a two-thirds probability of success. “That’s about 20 years at present-day emissions,” Millar said at the news briefing.
“These remaining budgets are substantially greater than the budgets that might have been inferred from the” IPCC, he added.
The recalculation emerges, said study co-author Joeri Rogelj of the International Institute for Applied Systems Analysis in Austria, because warming has been somewhat less than forecast by climate models — and because emissions have been somewhat more than expected.
“The most complex Earth system models that provided input to [the IPCC] tend to slightly overestimate historical warming, and at the same time underestimate compatible historical CO2 emissions,” he said by email. “These two small discrepancies accumulate over time and lead to an slight underestimation of the remaining carbon budget. What we did in this study is to reset the uncertainties, starting from where we are today.”
Pierre Friedlingstein, another author of the study and a professor at the University of Exeter in the United Kingdom, added at the news briefing that “the models end up with a warming which is larger than the observed warming for the current emissions. … So, therefore, they derive a budget which is much lower.”
Glen Peters, a senior research fellow at the Center for International Climate and Environmental Research, Oslo and a scientist with the Global Carbon Project, is firmly in the Global Warming Camp. He had this to say:
The IPCC consensus view indicates the carbon budget for 1.5°C is around 250 billion tonnes of CO2 from 2015.
Millar and colleagues suggest budgets of 730 billion tonnes of CO2 (RCP8.5), 880 billion tonnes CO2 (RCP2.6), and 920 billion tonnes CO2 using a simple carbon-carbon-cycle model, for carbon budgets from 2016 with a 66% likelihood.
Another study on 1.5°C emission pathways, finds the carbon budget over the period 2010-2100 is between 0-400 billion tonnes of CO2, which would be -200-200 billion tonnes CO2 from 2015-2100.
This gives carbon budgets for 1.5°C over 2016-2100, often from the same authors, ranging from -200 to 1000 billion tonnes of CO2. What a mess!
I can’t help but frame the paper in two ways:
- We understand the climate system, but a more careful accounting shows the carbon budgets are much larger.
- We don’t understand the climate system.
I have argued previously that 0.5°C makes a big difference to the carbon budget, and this is consistent with the IPCC carbon budgets.
This paper is going to have ripple effects. If their adjustments are correct, then those adjustments may cause inconsistencies elsewhere.
Do we have the climate sensitivity wrong?
We have known for years that the IPCC models have been projecting temperatures far above those actually experienced. We also know that average actual temperatures have been pushed higher by the recent record El Nino and associated spikes in sea surface temperatures via the warm phase of the Atlantic Multidecadal Oscillation (AMO) – further exacerbating disparities between model projections and actual results.
When one takes these factors into account, the 0.4 °C discrepancy between projected and actual temperature is made all the more large. Even more so if one makes the reasonable assumption that some portion of warming since the 19th Century is natural.
The Global Warming crowd has been playing fast and loose with the underlying numbers for years.
Now, even some proponents of Anthropogenic Global Warming are starting to admit the obvious.
The models are wrong. And they have been all along.
Our global climate is a staggeringly complex system with an enormous number of inputs – some of which we may not even know of. It has been changing for billions of years.
But exactly how it is changing – and how it will change – is knowledge that is currently beyond our grasp.
Now, some prominent scientists within the Global Warming crowd are finally beginning to admit this simple fact.
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