Climate Modellers Waiting for Observations to Catch Up with Their Predictions

Reblogged from Watts Up With That:

Guest essay by Eric Worrall

h/t Dr. Willie Soon; In climate science, when your model predictions are wrong, you wait for the world to correct itself.

New climate models predict a warming surge
By Paul VoosenApr. 16, 2019 , 3:55 PM

For nearly 40 years, the massive computer models used to simulate global climate have delivered a fairly consistent picture of how fast human carbon emissions might warm the world. But a host of global climate models developed for the United Nations’s next major assessment of global warming, due in 2021, are now showing a puzzling but undeniable trend. They are running hotter than they have in the past. Soon the world could be, too.

In earlier models, doubling atmospheric carbon dioxide (CO2) over preindustrial levels led models to predict somewhere between 2°C and 4.5°C of warming once the planet came into balance. But in at least eight of the next-generation models, produced by leading centers in the United States, the United Kingdom, Canada, and France, that “equilibrium climate sensitivity” has come in at 5°C or warmer. Modelers are struggling to identify which of their refinements explain this heightened sensitivity before the next assessment from the United Nations’s Intergovernmental Panel on Climate Change (IPCC). But the trend “is definitely real. There’s no question,” says Reto Knutti, a climate scientist at ETH Zurich in Switzerland. “Is that realistic or not? At this point, we don’t know.”

Many scientists are skeptical, pointing out that past climate changes recorded in ice cores and elsewhere don’t support the high climate sensitivity —nor does the pace of modern warming. The results so far are “not sufficient to convince me,” says Kate Marvel, a climate scientist at NASA’s Goddard Institute for Space Studies in New York City. In the effort to account for atmospheric components that are too small to directly simulate, like clouds, the new models could easily have strayed from reality, she says. “That’s always going to be a bumpy road.”

In assessing how fast climate may change, the next IPCC report probably won’t lean as heavily on models as past reports did, says Thorsten Mauritsen, a climate scientist at Stockholm University and an IPCC author. It will look to other evidence as well, in particular a large study in preparation that will use ancient climates and observations of recent climate change to constrain sensitivity. IPCC is also not likely to give projections from all the models equal weight, Fyfe adds, instead weighing results by each model’s credibility.

Read more: https://www.sciencemag.org/news/2019/04/new-climate-models-predict-warming-surge

It’s nice to learn that the IPCC is considering using observations to constrain model projections.

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A simple demo of order and chaos; Climate Models are not so simple

Here’s a fascinating example of oscillating systems.

In this demonstration 15 independent cyclic systems with different periods begin in phase, then watch how the total system departs from being in phase to apparent chaos to split phases and so on.

Now consider this demonstration as a model for all the contributors, big and small, to Earth’s climate–certainly more than the 15 billiard balls depicted here. And put the balls on springs of varying elasticity (permitting varying periods). And then allow the balls to hit each other (adding the third dimension to their oscillation and…..energy transfer).

Try to model and predict that!

In Aftermath of Volcanic Eruption, Photosynthesis Waxes, Carbon Dioxide Wanes

From Scientific American:

By Laura Wright on March 28, 2003

 

Read more from this special report:

A Guide to Volcanoes

In June 1991, when Mt. Pinatubo in the Philippines spewed tons of volcanic ash and gases into the atmosphere, it just so happened that halfway around the world scientists were beginning to obtain good data from carbon dioxide monitors high above the tree canopy in Harvard Forest, outside Boston, Mass. Now, more than a decade later, the measurements taken during the years following the eruption are providing new insight into how atmospheric aerosols affect photosynthesis. The findings, published today in the journal Science, are forcing scientists to rethink the factors that influence the cycling of carbon through the environment, particularly carbon dioxide, a major player in global warming.

 

Within three weeks of the Mt. Pinatubo eruption, the largest volcanic blast of the century, a band of sulfur aerosol had encircled the globe. By early 1992, the volcanic gases and aerosols had diffused through the stratosphere, veiling the earth. During that time, global carbon dioxide levels fell more sharply than any other decline on record. Some scientists suggested that global cooling caused ecosystem respiration to drop, lowering the amount of carbon dioxide emitted into the atmosphere. But Lianhong Gu of Oak Ridge National Laboratory, lead author of the Science report, didn’t think that could be the only explanation.

Gu knew that crop scientists had discovered that plants grow best in diffuse light. When sunlight is too intense, some leaves fall into shadow, unable to photosynthesize, while others bask in the direct beams but will reach a photosynthetic saturation point. Moderate cloud cover and aerosols block direct beams, but allow light to bounce back and forth off water vapor and other molecules, creating a “softer” light that reaches leaves that would otherwise be shaded. As a result, the plants photosynthesize more, using up carbon dioxide in the process. Gu and his collaborators determined that the same principles apply to forest canopies. The Harvard Forest data show that carbon dioxide levels dropped for two years following the eruption at Mt. Pinatubo findings that the scientists suggest represent a worldwide phenomenon given that the eruption had a global atmospheric effect. “Up until now we hadn’t linked aerosols and clouds with carbon studies,” Gu says. “In order to understand atmospheric carbon dioxide concentrations, which affect climate, we have to look at how aerosols and clouds affect the global carbon cycle.”

Predicting heat waves? Look half a world away

Reblogged from Watts Up With That:

[HiFast Note:  This study identifies the Madden-Julian Oscillation (MJO) and correlates one of its phases to California heat waves.  Nothing really new here.  Joe Bastardi has been talking about the MJO for many years.]

charles the moderator /

When thunderstorms brew over the tropics, California heat wave soon to follow

University of California – Davis

An orchard of young trees withstands drought in California's Central Valley in 2014. The ability to predict heat waves in the Central Valley could help better prepare and protect crops and people from the impacts. Credit UC Davis

An orchard of young trees withstands drought in California’s Central Valley in 2014. The ability to predict heat waves in the Central Valley could help better prepare and protect crops and people from the impacts. Credit UC Davis

When heavy rain falls over the Indian Ocean and Southeast Asia and the eastern Pacific Ocean, it is a good indicator that temperatures in central California will reach 100°F in four to 16 days, according to a collaborative research team from the University of California, Davis, and the Asia-Pacific Economic Cooperation (APEC) Climate Center in Busan, South Korea.

The results were published in Advances in Atmospheric Sciences on April 12.

FROM PREDICTION TO PROTECTION

Heat waves are common in the Central California Valley, a 50-mile-wide oval of land that runs 450 miles from just north of Los Angeles up to Redding. The valley is home to half of the nation’s tree fruit and nut crops, as well as extensive dairy production, and heat waves can wreak havoc on agricultural production. The dairy industry had a heat wave-induced economic loss of about $1 billion in 2006, for instance. The ability to predict heat waves and understand what causes them could inform protective measures against damage.

“We want to know more about how extreme events are created,” said Richard Grotjahn, corresponding author on the paper and professor in the UC Davis Department of Land, Air and Water Resources. “We know that such patterns in winter are sometimes linked with areas of the tropics where thunderstorms are enhanced. We wondered if there might be similar links during summer for those heat waves.”

The scientists analyzed the heat wave data from June through September from 1979 to 2010. The data were collected by 15 National Climatic Data Centers stations located throughout the Valley. From these data, the researchers identified 24 heat waves. They compared these instances to the phases of a large, traveling atmospheric circulation pattern called the Madden-Julian Oscillation, or MJO.

The MJO manifests as heavy rain that migrates across the tropical Indian and then Pacific Oceans, and researchers have shown that it influences winter weather patterns.

TROPICAL RAINFALL AND CALIFORNIA

“It’s well known that tropical rainfall, such as the MJO, has effects beyond the tropics,” said Yun-Young Lee of the APEC Climate Center in Busan, South Korea, the paper’s first author. “So a question comes to mind: Is hot weather in the Central California Valley partly attributable to tropical rainfall?”

Lee and Grotjahn found that, yes, enhanced rainfall in the tropics preceded each heat wave in specific and relatively predictable patterns. They also found that hot weather in the valley is most common after more intense MJO activity in the eastern Pacific Ocean, and next most common after strong MJO activity in the Indian Ocean.

“The more we know about such associations to large-scale weather patterns and remote links, the better we can assess climate model simulations and therefore better assess simulations of future climate scenarios,” Grotjahn said.

###

This work was supported by the National Science Foundation, the National Aeronautics and Space Administration, the Department of Energy Office of Science, the United States Department of Agriculture’s National Institute of Food and Agriculture, and the APEC Climate Center in the Republic of Korea.

A Simple Model of the Atmospheric CO2 Budget

Reblogged from Dr. Roy Spencer:

April 11th, 2019 by Roy W. Spencer, Ph. D.

SUMMARY: A simple model of the CO2 concentration of the atmosphere is presented which fairly accurately reproduces the Mauna Loa observations 1959 through 2018. The model assumes the surface removes CO2 at a rate proportional to the excess of atmospheric CO2 above some equilibrium value. It is forced with estimates of yearly CO2 emissions since 1750, as well as El Nino and La Nina effects. The residual effects of major volcanic eruptions (not included in the model) are clearly seen. Two interesting finding are that (1) the natural equilibrium level of CO2 in the atmosphere inplied by the model is about 295 ppm, rather than 265 or 270 ppm as is often assumed, and (2) if CO2 emissions were stabilized and kept constant at 2018 levels, the atmospheric CO2 concentration would eventually stabilize at close to 500 ppm, even with continued emissions.

A recent e-mail discussion regarding sources of CO2 other than anthropogenic led me to revisit a simple model to explain the history of CO2 observations at Mauna Loa since 1959. My intent here isn’t to try to prove there is some natural source of CO2 causing the recent rise, as I think it is mostly anthropogenic. Instead, I’m trying to see how well a simple model can explain the rise in CO2, and what useful insight can be deduced from such a model.

The model uses the Boden et al. (2017) estimates of yearly anthropogenic CO2 production rates since 1750, updated through 2018. The model assumes that the rate at which CO2 is removed from the atmosphere is proportional to the atmospheric excess above some natural “equilibrium level” of CO2 concentration. A spreadsheet with the model is here.

Here’s the assumed yearly CO2 inputs into the model:

1
Fig. 1. Assumed yearly anthropogenic CO2 input into the model atmosphere.

I also added in the effects of El Nino and La Nina, which I calculate cause a 0.47 ppm yearly change in CO2 per unit Multivariate ENSO Index (MEI) value (May to April average). This helps to capture some of the wiggles in the Mauna Loa CO2 observations.

The resulting fit to the Mauna Loa data required an assumed “natural equilibrium” CO2 concentration of 295 ppm, which is higher than the usually assumed 265 or 270 ppm pre-industrial value:

2Fig. 2. Simple model of atmospheric CO2 concentration using Boden et al. (2017) estimates of yearly anthropogenic emissions, an El Nino/La Nina natural source/sink, after fitting of three model free parameters.

Click on the above plot and notice just how well even the little El Nino- and La Nina-induced changes are captured. I’ll address the role of volcanoes later.

The next figure shows the full model period since 1750, extended out to the year 2200:

3
Fig. 3. As in Fig. 2, but for the full model period, 1750-2200.

Interestingly, note that despite continued CO2 emissions, the atmospheric concentration stabilizes just short of 500 ppm. This is the direct result of the fact that the Mauna Loa observations support the assumption that the rate at which CO2 is removed from the atmosphere is directly proportional to the amount of “excess” CO2 in the atmosphere above a “natural equilibrium” level. As the CO2 content increases, the rate or removal increases until it matches the rate of anthropogenic input.

We can also examine the removal rate of CO2 as a fraction of the anthropogenic source. We have long known that only about half of what is emitted “shows up” in the atmosphere (which isn’t what’s really going on), and decades ago the IPCC assumed that the biosphere and ocean couldn’t keep removing excess CO2 at such a high rate. But, in fact, the fractional rate of removal has actually been increasing, not decreasing.And the simple model captures this:

4
Fig. 4. Rate of removal of atmospheric CO2 as a fraction of the anthropogenic source, in the model and observations.

The up-and-down variations in Fig. 4 are due to El Nino and La Nina events (and volcanoes, discussed next).

Finally, a plot of the difference between the model and Mauna Loa observations reveals the effects of volcanoes. After a major eruption, the amount of CO2 in the atmosphere is depressed, either because of a decrease in natural surface emissions or an increase in surface uptake of atmospheric CO2:

5
Fig. 5. Simple model of yearly CO2 concentrations minus Mauna Loa observations (ppm), revealing the effects of volcanoes which are not included in the model.

What is amazing to me is that a model with such simple but physically reasonable assumptions can so accurately reproduce the Mauna Loa record of CO2 concentrations. I’ll admit I am no expert in the global carbon cycle, but the Mauna Loa data seem to support the assumption that for global, yearly averages, the surface removes a net amount of CO2 from the atmosphere that is directly proportional to how high the CO2 concentration goes above 295 ppm. The biological and physical oceanographic reasons for this might be complex, but the net result seems to follow a simple relationship.

Natural climate processes overshadow recent human-induced Walker circulation trends

Reblogged from Watts Up With That:

Institute for Basic Science

Normal conditions (top), strengthening due to natural variability (middle) and weakening due to greenhouse warming (bottom). Black arrows represent horizontal and vertical winds with the shading on the background map illustrating ocean temperatures. Over the past few decades, natural variability has strengthened the Pacific Walker circulation leading to enhanced cooling in the equatorial central-to-eastern Pacific (middle). Climate models forced by increasing greenhouse gas concentrations simulate weakening of the Walker circulation (bottom). (Right) Temporal evolution of model-simulated Walker circulation trends, with the dark blue line and orange shading denoting anthropogenically-induced changes and the impact of natural processes, respectively. Credit IBS

Normal conditions (top), strengthening due to natural variability (middle) and weakening due to greenhouse warming (bottom). Black arrows represent horizontal and vertical winds with the shading on the background map illustrating ocean temperatures. Over the past few decades, natural variability has strengthened the Pacific Walker circulation leading to enhanced cooling in the equatorial central-to-eastern Pacific (middle). Climate models forced by increasing greenhouse gas concentrations simulate weakening of the Walker circulation (bottom). (Right) Temporal evolution of model-simulated Walker circulation trends, with the dark blue line and orange shading denoting anthropogenically-induced changes and the impact of natural processes, respectively. Credit IBS

A new study, published this week in the journal Nature Climate Change, shows that the recent intensification of the equatorial Pacific wind system, known as Walker Circulation, is unrelated to human influences and can be explained by natural processes. This result ends a long-standing debate on the drivers of an unprecedented atmospheric trend, which contributed to a three-fold acceleration of sea-level rise in the western tropical Pacific, as well as to the global warming hiatus.

Driven by the east-west sea surface temperature difference across the equatorial Pacific, the Walker circulation is one of the key features of the global atmospheric circulation. It is characterized by ascending motion over the Western Pacific and descending motion in the eastern equatorial Pacific. At the surface trade winds blow from east to west, causing upwelling of cold water along the equator. From the early 1990s to about 2013, this circulation has intensified dramatically, cooling the eastern equatorial Pacific and triggering shifts in global winds and rainfall (see Figure 1). These conditions further contributed to drying in California, exacerbating mega-drought conditions and impacting agriculture, water resources and wild fires. Given these widespread impacts on ecosystems and society, the recent Walker circulation trends have become subject of intense research.

In contrast to the observed strengthening, the majority of climate computer models simulates a gradual weakening of the Walker Circulation when forced by increasing greenhouse gas concentrations (see Figure 1). “The discrepancy between climate model projections and observed trends has led to speculations about the fidelity of the current generation of climate models and their representation of tropical climate processes”, said Eui-Seok Chung, researcher from the Center for Climate Physics, Institute for Basic Science, South Korea, and lead-author of the study.

To determine whether the observed changes in the tropical atmospheric circulation are due to natural climate processes or caused by human-induced climate change, scientists from South Korea, the United States and Germany came together to conduct one of the most comprehensive big-data analyses of recent atmospheric trends to date. “Using satellite data, improved surface observations and a large ensemble of climate model simulations, our results demonstrate that natural variability, rather than anthropogenic effects, were responsible for the recent strengthening of the Walker circulation”, said Prof. Axel Timmermann, Director of the IBS Center for Climate Physics at Pusan National University and co-author of this study.

In their integrated analysis, the researchers found that the satellite-inferred strengthening of the Walker circulation is substantially weaker than implied by other surface observations used in previous studies. “Putting surface observations in context with latest satellite products was a key element of our study”, said co-author Dr. Lei Shi from NOAA’s National Centers for Environmental Information in the United States.

Analyzing 61 different computer model simulations forced with increasing greenhouse gas concentrations, the authors showed that, although the average response is a Walker circulation weakening, there are substantial discrepancies amongst the individual model experiments, in particular when considering shorter-term trends. “We found that some models are even consistent with the observed changes in the tropical Pacific, in stark contrast to other computer experiments that exhibit more persistent weakening of the Walker circulation during the observational period”, said co-author Dr. Viju John from EUMETSAT in Germany. The authors were then able to tease apart what caused the spread in the computer model simulations.

Co-author Prof. Kyung-Ja Ha from the IBS Center for Climate Physics and Pusan National University explains “Natural climate variability, associated for instance with the El Niño-Southern Oscillation or the Interdecadal Pacific Oscillation can account for a large part of diversity in simulated tropical climate trends”.

“The observed trends are not that unusual. In climate model simulations we can always find shorter-term periods of several decades that show similar trends to those inferred from the satellite data. However, in most cases, and when considering the century-scale response to global warming, these trends reverse their sign eventually”, said co-author Prof. Brian Soden from the Rosenstiel School of Marine and Atmospheric Science, at the University of Miami, United States.

The study concludes that the observed strengthening of the Walker circulation from about 1990-2013 and its impact on western Pacific sea level, eastern Pacific cooling, drought in the Southwestern United States, was a naturally occurring phenomenon, which does not stand in contrast to the notion of projected anthropogenic climate change. Given the high levels of natural decadal variability in the tropical Pacific, it would take at least two more decades to detect unequivocally the human imprint on the Pacific Walker Circulation (see Figure 1, right panel).

Solar variability weakens the Walker cell

Tallbloke's Talkshop

Credit: PAR @ Wikipedia
This looks significant, pointing directly at solar influences on climate patterns. The researchers found evidence that atmosphere-ocean coupling can amplify the solar signal, having detected that wind anomalies could not be explained by radiative considerations alone.

An international team of researchers from United Kingdom, Denmark, and Germany has found robust evidence for signatures of the 11-year sunspot cycle in the tropical Pacific, reports Phys.org.

They analyzed historical time series of pressure, surface winds and precipitation with specific focus on the Walker Circulation—a vast system of atmospheric flow in the tropical Pacific region that affects patterns of tropical rainfall.

They have revealed that during periods of increased solar irradiance, the trade winds weaken and the Walker circulation shifts eastward.

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Methane warming exaggerated by 400%

Reblogged from Watts Up With That:

By Barry Brill

The IPCC’s AR5 estimated the global warming caused by a tonne of livestock methane would be 28 times that of a tonne of carbon dioxide. New research destroys that estimate.

The war on meat has been gathering pace amongst our Western elites. The Economist makes a detailed case for “plant-based food” in the interests of quelling climate change –

The FAO calculates that cattle generate up to two-thirds of the greenhouse gases from livestock, and are the world’s fifth largest source of methane. If cows were a country, the United Herds of Earth would be the planet’s third largest greenhouse-gas emitter.

These calculations are based on figures supplied by the IPCC’s AR5, which contends that the global warming potential (GWP) of methane over 100 years is no less than 28 times the global warming it expects to be caused by an equivalent weight of carbon dioxide. This estimate is up from the GWP of 21 put forward in the IPCC’s previous report.

All this is now challenged by a new and authoritative research paper, Allen et al (2017): “A solution to the misrepresentations of CO2-equivalent emissions of short-lived climate pollutants, under ambitious mitigation”. This paper finds that conventional GWPs misrepresent the impact of short-lived gases (such as methane) on global temperature – and recommends the adoption of a new metric, denoted as GWP*.

This is a big advance. The abstract observes that, “measured by GWP*, implementing the Paris Agreement would reduce the expected rate of warming in 2030 by 28% relative to No Policy”. And who would know this better than lead author Myles Allen, who was also a co-author of the IPCC’s SR1.5 in 2018.

Currently visiting New Zealand, Professor Allen has recommended that enteric methane be entirely omitted from that country’s cap-and-trade scheme (ETS) because a steady-state herd of cattle can add very little to global warming. Methane has a half-life in the atmosphere of only about six years – so that every new molecule added is offset by the expiry of a molecule emitted by that herd a few years earlier.

He says:

“Traditional greenhouse gas accounting ignores the impact of changing methane emission rates while grossly exaggerating the impact of steady methane emissions”.   And –

“Climate policy the world over has traditionally treated every tonne of methane as supposedly “equivalentto 28 tonnes of carbon dioxide… It isn’t.

To find the carbon dioxide emissions that would actually have a similar impact on global temperature as methane emissions, you need to multiply those methane emissions by seven (not 28), and add the rate of change of methane emissions (measured in tonnes of methane per year per year), multiplied by 2100.”

If there is no “rate of change” (ie the quantity of emissions by weight is constant over time) then there is a one-off impact of only seven times the equivalent weight of CO2. Note that this should only be counted once – there is no accumulation as is the case for CO2 and other long-lived gases.

And, if the herd’s digestive efficiency is improved ever so slightly –

“Even more strikingly, if an individual herd’s methane emissions are falling by one third of one percent per year (that’s 7/2100, so the two terms cancel out) …then that herd is no longer adding to global warming. Yet if methane were included in a European-style Emission Trading System (ETS), the owner of the herd would have to pay just as if it was.”

Professor Allen is not beset by doubts regarding the error of the old ways:

“That this formula is vastly more accurate than the traditional accounting rule is indisputable.”

Not only are steady-state cattle herds climatically harmless, but they have the opportunity to help out the motorists and jet-setters. Professor Allen says in a further speech that if New Zealand reduced methane emissions by 30% over the next 30 years, that would actually contribute to global cooling:

“If a farmer is providing a service to the rest of the country by compensating for other people’s global warming, then that farmer might want to make a case that they should be compensated for that.”

As a co-author of SR1.5, the professor has a tip for the meat warriors that they should not rely on RCP scenarios:

“Those scenarios are based on economic models of the relative cost of different ways of reducing emissions. Some of the inputs to these models, like the estimated “cost” of a large fraction of the population turning vegetarian, are deeply subjective. The scenarios provide background information, but I would not rely on them as a basis for national policy.”

The findings of the Allen et al paper have been implicitly accepted by New Zealand’s Parliamentary Commissioner for the Environment, Simon Upton – formerly the head of the OECD Environment Directorate. He has this week published a lengthy and detailed report, Farms, Forests and Fossil Fuels, which recommends that the Government develop two separate targets for the second half of the 21st century – a zero target for fossil emissions, and a reduction target for biological emissions.

Let’s all enjoy a hearty guilt-free steak, served with lashings of cheese and butter!

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Why climate predictions are so difficult

“The difficulties [in climate modeling Bjorn Stevens of the Hamburg Max Planck Institute for Meteorology] and his fellow researchers face can be summed up in one word: clouds. The mountains of water vapor slowly moving across the sky are the bane of all climate researchers.”

Climate Etc.

by Judith Curry

An insightful interview with Bjorn Stevens.

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