New method could improve atmospheric forecasts over months, decades, and could explain 'pause' in global warming

August 18, 2015 by Vincent Allaire, McGill University

The atmosphere is so unstable that a butterfly flapping its wings can, famously, change the course of weather patterns. The celebrated "butterfly effect" also means that the reliability of weather forecasts drops sharply beyond 10 days.

Beyond this, there are strong fluctuations in temperature, with increases tending to be followed by decreases, and vice-versa. The same pattern holds true over months, years and decades. "This natural tendency to return to a basic state is an expression of the 's memory that is so strong that we are still feeling the effects of century-old fluctuations," says McGill University physics professor Shaun Lovejoy. "While man-made atmospheric warming imposes an overall increasing trend in temperatures, the natural fluctuations around this trend follow the same long memory pattern."

In a new paper published online in Geophysical Research Letters, Lovejoy shows how to directly harness the atmosphere's elephantine memory to produce temperature forecasts that are somewhat more accurate than conventional numerical computer models. This new method, he says, could help improve notoriously poor seasonal forecasts, as well as producing better long-term climate projections.

Improvement on standard approach

To take advantage of the butterfly effect, Lovejoy's approach treats the weather as random and uses historical data to force the forecast to reflect a realistic climate. This allows it to overcome limitations of the standard approach, in which imperfect representations of the weather push a computer model to be consistent with its model climate - rather than with the real . The new method also represents an improvement over other statistical forecasting techniques that exploit only the atmosphere's short-term memory, Lovejoy asserts.

Lovejoy's paper uses a simple version of his new method to show that the so-called pause in global warming since 1998 can be well explained with the help of historical atmospheric data. He also concludes that this method proves more accurate over this period than the standard computer models used, for example, by the International Panel on Climate Change.

Lovejoy's model also predicts that if continue at the post 2000 rate, there is a 97.5% chance that the "pause" in global warming will be over before 2020.

Explore further: Global warming 'pause' since 1998 reflects natural fluctuation, study concludes

More information: Lovejoy, S. (2015), "Using scaling for macroweather forecasting including the pause", Geophys. Res. Lett., 42, DOI: 10.1002/2015GL065665

Related Stories

Macroweather is what you expect

February 25, 2013

While short-term weather is notoriously volatile, climate is thought to represent a kind of average weather pattern over a long period of time. This dichotomy provides the analytical framework for scientific thinking about ...

Mars, too, has macroweather

November 13, 2014

Weather, which changes day-to-day due to constant fluctuations in the atmosphere, and climate, which varies over decades, are familiar. More recently, a third regime, called "macroweather," has been used to describe the relatively ...

Recommended for you

Galactic center visualization delivers star power

March 21, 2019

Want to take a trip to the center of the Milky Way? Check out a new immersive, ultra-high-definition visualization. This 360-movie offers an unparalleled opportunity to look around the center of the galaxy, from the vantage ...

Physicists reveal why matter dominates universe

March 21, 2019

Physicists in the College of Arts and Sciences at Syracuse University have confirmed that matter and antimatter decay differently for elementary particles containing charmed quarks.

13 comments

Adjust slider to filter visible comments by rank

Display comments: newest first

MR166
2 / 5 (8) Aug 18, 2015
Oh yea, "The Pause" does not even exist according to 97% of the climate scientists. Why do the continue to explain something that does not exist away????
leetennant
3.5 / 5 (8) Aug 18, 2015
I can't imagine Lovejoy's paper is as incoherent as this article. Who is writing these things? What's Lovejoy's new method? How does it work? What differentiates it from others? I still have no clue. And, as MR166 points out, there was never really a "pause" so I guess what he's saying is that his new method better-accounts for normal variations such as the ENSO cycle? If that's the case, how would it be "over by 2020" when we're in an El Nino now? Because 2020 is when oceans have warmed sufficiently to stop absorbing the extra heat? No clue. This is terrible reporting.
nevermark
3.7 / 5 (9) Aug 18, 2015
@leetennant, It is difficult to tell from the article, but it sounds like some basic know properties of real weather are being used as constraints on predictions.

If so, a good analogy are 3 body simulations. If you numerically simulate a 3-body system in space small numerical differences/errors accumulate slowly but then blow up so that eventually (after many many simulation years) slightly different simulations produce very different results.

One way to improve the accuracy of those simulations is to repeatedly normalize the energy of the system, since we know in real systems energy can't appear or disappear. This doesn't eliminate numerical problems completely, but reduces them.

That's my take on the article anyway.
leetennant
4 / 5 (8) Aug 18, 2015
Thanks, @nevermark. I could, of course, read the paper it's based on but I read sites like this so I don't have to read every single paper on every subject. What you've explained makes sense. It certainly beats the downright bizarre:

"Lovejoy shows how to directly harness the atmosphere's elephantine memory..."
nevermark
3.4 / 5 (10) Aug 18, 2015
Oh yea, "The Pause" does not even exist according to 97% of the climate scientists. Why do the continue to explain something that does not exist away????


Nobody disputes that atmosphere temperatures rose more slowly for a period of time.

The issue is whether climate energy accumulation actually slowed down or is normal noise due to dynamics (in accumulation or in exchanges between atmosphere and upper and/or lower ocean).

A glance at any past temperature record shows similar variability on top of the main trend.

Nobody is predicting climate change so fast it out runs dynamics. Not even the direst warnings suggest that will ever happen.
runrig
4.2 / 5 (5) Aug 19, 2015
What I think this "method" involves is constraining a forecast within the bounds of normal climatology. That is by saying in effect that a forecast outcome within the forecast period is not credible due to it never having happened before and amending it to fit history. this in the sense of natural variability and not any ongoing ave temp rise due to AGW. This is already done in weather forecasting via intervention by senior forecasters on the NWP model output (ie not integrated into the model implicitly).
This is fine for fairly short-term forecasts (decade or 2 ) but obviously not over the extreme long term, unless some sort of rate-of-change of climatology could be calculated/applied.
jeffensley
2 / 5 (4) Aug 19, 2015
Forecasting by looking backward... it's of course the best we can do but in a climate that is changing, how valuable are old standards when attempting to make predictions?
denglish
2.6 / 5 (5) Aug 19, 2015
Unfortunately, this paper is behind a pay-wall.

I find it disappointing that the hiatus is giving so many fits. It exists, it doesn't exist...what is it? How does it fit into the Karl et. al. paper, and will that need to be unraveled now?

We're all over the place. This isn't' a bad thing; everyone stats somewhere. However if anything is demonstrated, it is that we don't have even close to enough expertise in climate science to impose ruinous economic policies and engage in morally corrupt group-think.
denglish
2.6 / 5 (5) Aug 19, 2015
the reliability of weather forecasts drops sharply beyond 10 days.

That helps explain why the CMIP5 models have failed.

we are still feeling the effects of century-old fluctuation

I wonder if that was accounted for in CMIP5.

as well as producing better long-term climate projections

You mean they're not perfect?

imperfect representations of the weather push a computer model to be consistent with its model climate - rather than with the real climate.

You don't say.

that the so-called pause in global warming since 1998 can be well explained with the help of historical atmospheric data

So the Earth has been heating and cooling as part of its normal life cycle.

97.5% chance that the pause in global warming will be over before 2020.

So there is a pause, right? No? Make up my mind!

At least we have a verifiable prediction.

AGW: this would be funny if not so sad.

Eddy Courant
3.7 / 5 (3) Aug 20, 2015
We can all agree on one thing. That we just don't know what that is.
denglish
3 / 5 (4) Aug 20, 2015
We can all agree on one thing. That we just don't know what that is.

Exactly. We can also say that what the earth is doing has not surpassed any boundaries of normal cyclic climate variations.

This makes the ruinous economic policies and morally corrupt science that we are experiencing even more absurd.
Mike_Massen
1.8 / 5 (5) Aug 23, 2015
Re: denglish, cherry picks with nil idea of Robust Statistics
https://en.wikipe...atistics

Acts like ubavontuba, similarities abound. Key issue they both fail, other than statistics/means/medians etc are failures to understand key settled physics
https://en.wikipe...transfer

further detailed re greenhouse gases here
https://en.wikipe..._forcing

Is well proven, never refuted. So question arises Where is the heat going, answer is obvious to anyone who has done high-school physics - the material with the higher specific heat/mass. That is, Oceans !

denglish's reporting is an outright lie, his naive attempt to pursue propaganda here, Eg my last post
http://phys.org/n...ght.html

denglish FAILs to address the warning by RSS
http://www.remss....eratures

ie Last sentence of 1st para
Forestgnome
3 / 5 (2) Aug 23, 2015
Farmer's Almanac. Already been done.

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.