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In a reversal, climate scientists now say goal set in Paris accord is within reach

REUTERS/Charles Platiau
The Paris Agreement’s goal of holding the line on Earth’s rising temperature to 1.5 degrees Celsius is in fact possible… but challenging.

With hopeful news on global warming being such a rarity, it’s worth a few minutes to consider one of the more prominent recent retreats from total gloom.

In an analysis published Friday in the respected journal Nature Geoscience, a team of chiefly British scholars concludes that the Paris Agreement’s goal of holding the line on Earth’s rising temperature to 1.5 degrees Celsius in fact possible.

Possible … but challenging. Challenging … but maybe not as excruciating as it looked at the time the global goal and national targets were established in December 2015.

Back then, the climate economist Michael Grubb of University College London was widely quoted as saying the only conceivable pathways to success would require cutting carbon dioxide emissions at a pace “incompatible with democracy.”

As it happens, the same Michael Grubb is an author of the new paper, which finds that fresher data on the pace of CO2 emissions reduction and adoption of non-fossil-fuel energy systems — along with a significant recalculation of how much more CO2 the atmosphere can handle before going over 1.5°C — put the Paris goal within reach.

As you might expect, the deniers are having a field day with this shift in outlook, as they do with anything susceptible to being portrayed as error by those know-it-all climate scientists.

As for Grubb, he told The Times of London:

When the facts change, I change my mind, as [the economist John Maynard] Keynes said. It’s still likely to be very difficult to achieve these kind of changes quickly enough but we are in a better place than I thought.

The key fact that has changed in the view of Grubb and fellow authors is the pace of warming since the beginning of this millennium, which they now find to be somewhat slower than the forecast used in the Paris talks, and derived from a suite of used models by the Intergovernmental Panel on Climate Change.

This reflects a variety of factors, the largest including faster-than-expected adoption of clean energy alternatives and larger-than-expected reductions in the growth of new emissions in in some large industrial economies, especially China’s. Smaller factors also played a role, including a longer-than-expected persistence of reflective atmospheric particles that block incoming solar radiation.

Expanding the 'carbon budget'

Taken together, the adjustments mean that the “carbon budget” — how much more carbon we can load into the atmosphere without pushing the temperature increase about 1.5°C — is far greater than the 70-gigaton figure used in the Paris discussions, which would have been used up in five years or less. Now it’s looking more like 240 gigatons.

If the planet stays within that budget, and continues on its current path of controlling methane and other globe-warming gases, the team calculates a two-in-three chance of staying under 1.5°C above pre-industrial levels, or about another 0.6°C above today’s temperatures.

From Oxford University’s announcement of the findings:

Three approaches were used to evaluate the outstanding 'carbon budget' (the total amount of CO2 emissions compatible with a given global average warming) for 1.5°C: re-assessing the evidence provided by complex Earth System Models, new experiments with an intermediate-complexity model, and evaluating the implications of current ranges of uncertainty in climate system properties using a simple model. In all cases the level of emissions and warming to date were taken into account.

Dr. Richard Millar, lead author and post-doctoral research fellow at the Oxford Martin Net Zero Carbon Investment Initiative at Oxford University, said: "Limiting total CO2 emissions from the start of 2015 to beneath 240 billion tons of carbon (880 billion tons of CO2), or about 20 years' of current emissions, would likely achieve the Paris goal of limiting warming to 1.5°C above pre-industrial levels."

"Previous estimates of the remaining 1.5°C carbon budget based on the IPCC 5th Assessment were around four times lower, so this is very good news for the achievability of the Paris targets," notes Professor Pierre Friedlingstein of the University of Exeter, a co-author on this study and a key expert on carbon budgets for the Intergovernmental Panel on Climate Change (IPCC).

Achievable does not mean simple or easy, of course. The Nature Geoscience paper says that “limiting warming to 1.5°C is not yet a geophysical impossibility, but is likely to require delivery on strengthened pledges [under the Paris accord] for 2030 followed by challengingly deep and rapid mitigation.”

After noting that emissions reductions along the lines deemed necessary by the IPCC have only occurred in circumstances like the America’s depression of the 1930s and the collapse of the Soviet Union, the paper says,

More ambitious near-term mitigation may be more feasible than previously thought. The rapid growth of global emissions from 2000 to 2013 was dominated by increases in Chinese emissions, driven, at least in part, by unprecedented levels of debt-fuelled investment in carbon-intensive industries and capital stock. Sustaining such expansion is likely to be neither necessary (the infrastructure is now built) nor feasible (the debt levels are likely to prove unsustainable).

For these reasons, the possibility that both Chinese and global emissions are at or near their peak, and could reduce from 2020, seems less far-fetched than it once did. This could allow for the required strengthening of the [national goals laid out in Paris] … more readily consistent with a 1.5°C goal.

Experts endorse the shift

Expert reaction to the study appears to be generally favorable in assessing the methods and supportive in endorsing the authors’ cautions against irrationally exuberant optimism. A sampling:

David Shukman, science editor for BBC: “The [climate] models are simulated approximations of possible futures. Inevitably they are going to be at least slightly adrift of reality, either in the amount of warming or its timing….  In many ways, it's remarkable that these computer constructs are even roughly on track. And models designed to come up with very broad potential outcomes for the end of the century may not be fine-tuned enough to give more detailed forecasts year-by-year.

“The authors themselves are anxious that their research is not misunderstood. The need for urgent action to reduce emissions is unchanged, they say. It's just that the most ambitious of the Paris Agreement targets is not as unachievable as many once thought, that there is time to act, though the task remains a monumental one.”

Ankur Desai, professor in atmospheric and oceanic sciences at University of Wisconsin—Madison, to The Weather Channel: “The study is correct to note that rates of adoption of non-carbon polluting energy sources and fossil fuel emissions reductions are occurring faster than projected in many places. There is a revolution occurring in energy in response to consumer demand and government incentives. However, whether these trends can lead to meeting the more ambitious climate targets of no more than 1.5°C warming is difficult to expect unless nations put teeth into the voluntary emission reduction pledges they all made at Paris…. While not geophysically impossible, it is likely politically implausible, though not outside the reach of possibility."

Kevin Trenberth, senior scientist at the U.S. National Center for Atmospheric Research, also to the Weather Channel: “Right now, the track we're headed on, we'll double carbon dioxide before 2060 which would correspond to 2°C and that’s the problem. I don't think 1.5°C is achievable, I think 2°C is achievable."

* * *

The full paper, “Emission budgets and pathways consistent with limiting warming to 1.5°C,” can be found here but access is not free.

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Comments (19)


There are two sides to just about every scientific theory. Since the global warming issue is emotional, those on the other side are called ‘deniers.’ Name calling does nothing but widen the divide. Global warming is a theory. Predictions are theoretical and they will change.

Predictions are often based on yesterday’s technology. The human desire to do good and to invent is not properly included in the equations. Technology does not grow, it explodes, and once green technology takes hold, there is no going back.

Through education, more and more people are made aware. Awareness changes behavior, behavior changes the solution, and the solution changes the forecasts. Tomorrow’s technology is where the conversation should be.

Where do I start

The idea that there are two sides to every scientific theory is false. There may be one, there may be many sides - scientific theories are based on evidence. In some areas of science the evidence is conclusive, and others less so, and the soundness and consensus of the theories varies accordingly.

You also have a misunderstanding of what a scientific theory is - like many others, you are hung up on the term "theory" as something that is always open to change. Gravity is a theory, but it isn't going to change. Evolution is a theory, but it is not in any scientific dispute. There is dispute about the extent and rate of climate change, but it is undeniable that man has altered the climate. That won't change either.

The reason that certain people are called deniers is not because its an emotional issue - its because they are denying the evidence. A better term would be "liars" not dividers. When one side is basing its theory on facts and evidence, and the other side is simply lying, there are not two sides and the divide is not something that can and should be bridged.

I wish people were becoming more aware through education. Your comment demonstrates a lack of scientific understanding, which unfortunately is very widespread.

Well, to answer you Pat, you should have started somewhere else

There is no consensus on Gravity. The theory is well defined down to x number of digits, and after that, there is debate. It is the same with any theory. At some level of precision there is error. Just google the Hawkins-Susskind debate and you will find a treasure-trove of insight.

Climate change predictions? Some show the temperature skyrocketing while others show it evening out in ten years, then dropping. Most theories are in the middle somewhere. To be handed this much uncertainty and have only 3% of scientists disagree, I’d say that is pretty good. What confuses me is why so much attention is paid to that 3%. Seems like a waste of time. And to throw insults and condescending remarks around like you do, it sounds like an emotional subject.

I am wondering if you have taught college-level science as I have. And if you have, do you insult those students who do not agree with you? Seems like a losing proposition for both sides. When you insult someone who does not believe in climate change, it makes them less likely to adapt to green technology. Please keep it conversational.

Climate change is extremely complex and many numbers are very approximate. We have more to learn than we know. It was not specifically stated in the article, but scientists were off by a factor of over 3 on the amount of carbon the atmosphere can hold. A factor of 3! That’s not an adjustment, that’s huge! How does that affect ocean absorption? How does that affect long-term forecasts? We cannot know the answer to any definite degree, but we can point in a direction. Meanwhile, the science is exciting and the wager is high.


Again, yes, there is a debate about the extent and effect of climate change. But there is no scientific dispute that man has affected the climate.

And there is nothing insulting or non-conversational about pointing out lies. And that is what climate change denialists are doing - telling bald-faced lies. Debate about the extent of man-made climate change is exciting. But giving credence to people telling flat-out lies is not.


And is far as the approach goes, I don't have a good answer for dealing with people who misrepresent or ignore actual science. Will people be put off if you point out what they are saying is false? Often, I think, yes. But you can't really reach middle ground with people not interested in legitimate debate. And you certainly shouldn't pretend their positions are legitimate when they aren't.

not a theory

Global warning is a fact, not a theory. Temperatures are increasing. If you choose to simply disbelieve all the data compiled over the last several decades, we're not having a rational discussion.

The rate at which this is happening, what's causing it, and what might work to reduce it, are all topics for "theory" at this point. But the actual warming is not. It's already happening.

I don't know what you mean by "two sides to just about every scientific theory". Unless you're talking about theories that are the subject of ginned-up controversies by partisan, for-profit media companies.

"Fresher data"

"Fresher data" "Recalculation"....In fact, the report says the climate models are wrong, but we cant say that out loud, can we, because that's what those deniers have been saying all along.


You could say it out loud - you'd just be wrong. I know that Breitbart published a wholly false story on this, which its generally ill-informed and scientifically illiterate readership will gladly regurgitate.

The thing about science is that its based on evidence, and when new evidence emerges, science will react to that new evidence. That's completely different than what the deniers are doing, which is denying evidence.


But Terry....consensus!

Seriously though, you have elucidated what the people labelled "deniers" have said since day 1.

We have an issue; we are not sure how bad it is, or if its bad at all; we don't know why its happening, how to stop it, or if we can stop it....there simply isn't enough solid data, what you call evidence.

I have never read Brietbart, I read the report.

Skepticism is an inherent part of science. When skeptics are villified for doing the part they rightfully play, the theory being postulated is inherently discredited. It seems you understand these things.


There is not a consensus about the extent of the effect of climate chance, but there is consensus that man has effected the climate. There is enough solid data to support that - to say otherwise is a lie.

Skepticism is a very important part of science. But misrepresenting science and/or outright lying is not the same as skepticism. Skeptics aren't being villified. Liars are being villified. Big difference.

Oh for crying out loud.

If you can't comment on a scientific issue without betraying your ignorance don't waste our time. The report did not say the model was wrong. Models are adjusted and refined all the time. Doesn't mean they are wrong, but does mean they can be improved. In addition, had you read the article, the study authors point out that one of the issues is the faster adoption of clean technologies and lower than expected increases in major countries emissions. That's changing the inputs, put doesn't change the model.

All models are "wrong"

The only correct model would be a duplicate Earth we can pour CO2 into as a controlled experiment.

There is the famous quote from George Box - "all models are wrong, but some are useful". The models they have now are wrong, but they are useful.

Since we only get one Earth we should be more careful how we treat it.The people claiming ignorance should be the most paranoid about changing the climate. If we really "don't know" then an absolute catastrophe is as likely as no impact whatsoever but the risk to people is quite different with those possibilities. Better to be conservative and reduce emissions. Unfortunately humans have been shown scientifically to be quite awful at assessing risk.

Thank you, Mr. Meador, for

Thank you, Mr. Meador, for bringing this to MinnPost’s readers’ attention. To make it easier, I’d like to summarize the results of the study: The previous projections of the climate change were incorrect and now they are corrected to the better. The reason is that assumptions for previous projections happened to be incorrect, both for nature’s reaction and human progress.

Now, a reasonable question is, of course, how can we be sure that current assumption are correct and that in five years this projections will not be corrected to the better again? And if that is a possibility, what value does the current projection have, especially for a hundred years forward?

How can we sure

that in five years the projections will not be corrected to the worse? How much more arctic ice will have melted by then, and how many more hurricanes, exacerbated by warmer oceans, will have wrought destruction on fragile ecosystems and human lives?

The previous projections were not "incorrect"; they were projections based on what was known at that time to put into the model. Current projections could also be "corrected" based on what is occurring now. I'm not holding my breath that the situation is improving.

“in five years the

“in five years the projections will not be corrected to the worse?” We do not which was exactly my point: since we don’t know what will happen, we should not be acting as if the sky is falling. All I was saying was that predictions for a hundred years ahead are more of a guess than science because parameters are changing and new parameters are being added. In other words, we don’t know much more than we do… So no reason to panic: it never creates good decisions. This is common sense and logic. Maybe it is more reasonable to concentrate on saving California from inevitable mega-earthquake..

“…how many more hurricanes, exacerbated by warmer oceans…” Will you please explain to me how come we did not have a strong hurricane in more than a decade even though oceans are apparently warming?

That is a terrible approach

If you don't know the answer and the risk is extinction you should prepare for the worst instead of hoping for the best. We have the ability to change things to mitigate the impact but instead we are deciding to take our chances with the status quo and hope the experts are wrong.

I am afraid you misunderstood

I am afraid you misunderstood me. I am all for recycling, reusing, renewable energy, and anything else such as this All of the above are reasonable measures. What I am against is being told that climate change is the greatest threat to the humankind at a time of terrorism, wars, nuclear North Korea, potential mega-quake in California, possible meteor hitting Earth, etc. All those things are already deadly and may be even deadlier in the very near future so doing drastic things to prevent something that there is no scientific way to predict is not rational. I am against acting because of pure fear rather than logic and against people instilling that fear by unreasonably connecting natural disasters to climate change…

Climate Scientists vs A Few Climate Scientists

The proper headline of the article should read "A few climate scientists..."

This is a very misleading article as it alludes to speak for all climate scientists. Also, by merely raising the "carbon budget" to remain below 2 degrees Celsius from 71 to 240 gigatons seems like a very flimsy claim without an extensive investigation of the author's assertion.

There are multiple points of view within the climate scientist community. Many point out that we will only avoid surpassing 2 degrees or even 4 degrees Celsius by not only stopping CO2 pollution but also through aggressive geo-engineering. Their claim is due to the fact that the Arctic is rapidly melting and releasing massive amounts of methane. They claim this will only accelerate with time irrespective of CO2 reduction.

One scientist, Dr. Natalia Shakohova, has done significant primary research doing ice borings in Siberia and has documented several mechanisms which methane is erupting. (Please see Nature Communications, June 22, 2017. ).

In another press release she also went out on a limb and made the claim that we are in the midst of the 50 gigaton methane eruption. This assertion, unfortunately, is merely a guesswork based upon her observed events in the field, but in my mind is much better than someone hiding in an office looking at old composite data.

Another ice scientist, Dr. Peter Wadhams, who has done significant primary research, has published a book "Farewell to Ice" in which he as calculated the devastating consequence of the loss of Arctic albedo, which he estimates will be completely gone during the summer by 2023. Whether his calculation is correct or not, in my opinion is irrelevant since enough of the permafrost in the Arctic is already disintegrating rapidly that we are already at the beginning of a runaway climate scenario.

It is therefore impossible for the climate scientist referred by the article's author to have consensus agreement of "climate scientists". What makes his claim even more tenuous is that his findings are hidden behind a pay wall which makes it very difficult to verify or criticize his hypothesis.

The above article and it's headline, however, presents them as statements of fact.

Finally, one does not have to rely on derivative statements of people behind a pay wall and can actually observe the devastation in action. For example, on the website , one can look across the planet in almost real time at the fractured jet streams due to loss of Arctic albedo, and the stalled highs, lows, and consequential droughts, forest fires, floods, and hurricanes. One can also observe warm ocean temperatures, warm currents invading the Arctic and get a good sense of the fire that's ongoing within our home.

I do not propose that we throw our hands up in surrender, but we cannot allow ourselves to sink into complacency and continue to pump out CO2, because a couple people assert that we are within a "carbon budget".

Unfortunately, it's not true

While the headline of the study implies that we can still stay under +1.5°C warming, the study does not actually say that. First, the baseline of the study (zero warming) is mid-1800's not late 1800's like most climate scientists use. Second, the study's definition of +1.5ºC is where it first happens, not where it peaks. In other words, it's a technical definition, not the one you care about in real life. For a detailed explanation see:

We need to work hard to stay under +2ºC warming... but we are not doing much. We could fix climate change "for free" by putting a price on carbon. See my TEDx talk on that: