Ozone recovery is offsetting Southern Hemisphere climate change trends in summer
Cooler summers in Australia despite high CO2 levels!
If the latest climate report from the Intergovernmental Panel on Climate Change (IPCC) made anything clear, it was that much more needs to be done to reverse the impacts of climate change.
But buried in the 1,000-page document of mostly alarming reading there was one positive gem.
Our action in reducing ozone depletion is, in the short term, offsetting some of the impacts greenhouse gases are having on summer rainfall systems in the Southern Hemisphere.
What does that mean?
It's all to do with a major climate driver known as the Southern Annular Mode (SAM), a belt of strong westerly winds linked to rainfall in the Southern Hemisphere.
The SAM's position — either moving further north or south — can influence which latitudes see the impacts of storm systems and cold fronts, and can also have an influence on temperature.
Without ozone depletion and greenhouse gas emissions, its position over the southern ocean has a natural variability both north and south.
But with those things occurring, the SAM has been trending further south toward Antarctica, research has shown.
With the SAM further south, storm tracks also shift south, away from Australia — changing which areas recieve rainfall.
Australian Antarctic Division principle research scientist Andrew Klekociuk said in the last 20 years however, ozone recovery has been turning that trend around during the summer months, pushing back on the influence of greenhouse gases.
"[Ozone recovery] is starting to relax the change that we’ve seen [in the SAM]," Dr Kelkociuk said.
"For a period now, we have this tug-of-war between ozone recovery and the effects of greenhouse gas increases."
The weakening of the pole-ward trend during the summer months was referenced in the latest IPCC report, released last month.
It's an element of the report climate science professor Julie Arblaster, from Monash University, described as a "really good news story".
"We, as humans, are doing a big chemistry experiment on our planet at the moment and anything we can do to reduce our impact on the climate system has to be of benefit," she said.
"Bringing the [rainfall and storm systems] back equator-ward would certainly help return some of the rainfall patterns to their normal location."
What could this mean for rainfall?
The position of the SAM has different rainfall outcomes for different parts of the Southern Hemisphere and Australia.
Some regions, including eastern Australia, actually experience wetter conditions in summer when the wind-belt is further towards Antarctica.
That means for eastern Australia, a reversal of that trend could mean less rainfall during the summer months, according to Professor Arblaster.
Regions like western Tasmania and New Zealand, however, could see rainfall increase.
But Professor Arblaster said it was hard to say exactly what the pushback means for Australian summer rainfall, because the SAM was not the only factor influencing the weather.
"Different regions have influences from many things and not just the SAM trend," she said.
"For example, the El Nino Southern Oscillation.
"So there is a strong understanding of how the ozone hole has affected the SAM, but how much influence ozone depletion has had on Australian rainfall trends is still a question."
Impact to temperatures
When it comes to temperatures, Professor Arblaster said there was evidence international efforts to limit ozone depletion had also gone a long way in "avoiding" larger temperature rises across the globe.
"The ozone-depleting substances are really strong greenhouse gasses," she said.
"So if we had continued emitting CFCs, then a study by Goyal and co-authors found that would have led to an additional warming of 0.5 and 1 degree up to now in some regions, and additional warming after."
Short-term buffer only
Both the IPCC report, Professor Arblaster and Dr Klekociuk made one thing clear.
The buffer that ozone recovery was providing to the pole-ward shift of the SAM would not last if greenhouse gas emissions were not reduced.
"If we don’t reduce emissions soon, the greenhouse gases will overwhelm any impact from ozone recovery by the end of the 21st Century," Professor Arblaster said.
The Antarctic ozone hole has recently started to show signs of recovering since The Montreal Protocol was signed in the late 1980's — an international agreement to phase out the use of ozone-depleting substances such as chlorofluorocarbons (CFCs).
It is currently on track to have recovered by the mid to late 21st Century.
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Climate change: Arctic WARMING linked to COLDER winters
But Warmists can explain anything away
A new study shows that increases in extreme winter weather in parts of the US are linked to accelerated warming of the Arctic.
The scientists found that heating in the region ultimately disturbed the circular pattern of winds known as the polar vortex.
This allowed colder winter weather to flow down to the US, notably in the Texas cold wave in February.
The authors say that warming will see more cold winters in some locations.
Over the past four decades, satellite records have shown how increasing global temperatures have had a profound effect on the Arctic.
Warming in the region is far more pronounced than in the rest of the world, and has caused a rapid shrinkage of summer sea ice.
Scientists have long been concerned about the implications of this amplification of global change for the rest of the planet.
This new study indicates that the warming in the Arctic is having a significant impact on winter weather in both North America and East Asia.
The researchers detail a complex meteorological chain that connects this warmer region to a rotating pattern of cold air known as the polar vortex.
The authors show that the melting of ice in the Barents and Kara seas leads to increased snowfall over Siberia and a transfer of excess energy that impacts the swirling winds in the stratosphere above the North Pole.
The heat ultimately causes a stretching of the vortex which then enables extremely cold weather to flow down to the US.
There has been an increase in these stretching events since satellite observations began in 1979.
The scientists believe this vortex stretching process led to the deadly Texas cold wave in February this year.
"We're arguing that melting sea ice across Northwest Eurasia, coupled with increased snowfall across Siberia is leading to a strengthening of the temperature difference from west to east across the Eurasian continent," explained lead author Dr Judah Cohen, who's a professor at the Massachusetts Institute of Technology (MIT) and a director of Atmospheric and Environmental Research, a weather risk management company.
"We know when that temperature difference increases, that leads to more disruptions of the polar vortex. And when it's weakened, that leads to more extreme winter weather such as the Texas cold wave last February."
The researchers say that their findings are based on both observations and modelling and they show a physical link between climate change in the Arctic, the stretching of the polar vortex and the impacts on ground.
The authors believe their work could improve predictions about the onset of extreme cold winter events.
"One of the benefits of this study is that if you recognise these precursors and you know the conditions that are favourable for triggering such event, then you get to extend your forecast lead time," said Dr Cohen.
"In Texas, people could have certainly prepared better with better warnings, some people froze to death in their homes and perhaps they could have gone to seek shelter."
Looking at the bigger picture, the research team believes that their findings will help people understand that global warming is complex and perhaps dispel the idea that colder winters mean climate change isn't happening.
"There has been a long-standing apparent contradiction between the warmer temperatures globally, however, an apparent increase in cold extremes for the United States and in northern Eurasia. And this study helps to resolve this contradiction," said fellow author, Prof Chaim Garfinkel from the Hebrew University of Jerusalem.
"In the past, these cold extremes over the US and Russia have been used to justify not reducing carbon, but there's no longer any excuse to not start reducing emissions right away."
https://www.bbc.com/news/science-environment-58425526
********************************************Those pesky clouds
That clouds would warm the earth was an integral part ofthe original global warming theory
Best estimates for global temperature increases due to a doubling of atmospheric CO2 since the start of the industrial era are between +1.5C and +4.5C. A major reason for this huge range of uncertainty is how clouds will perform in a warmed world, with some modelers saying clouds will help cool the planet, while the majority say clouds will further warm it.
Clouds add immense uncertainty to climate models because they contain so many variables (including altitude, size, turbulence, amount of ice crystals, quantity and particle chemistry), and also because they don’t fit neatly inside the global grid cell system that modelers use to estimate warming.
A new study used a machine learning model to bypass previous cloud modeling problems. The researchers concluded that a doubling of atmospheric CO2 will most likely lead to a 3.2C (5.76F) global temperature increase, almost exactly in the middle of the range estimated by the majority of current U.N. Intergovernmental Panel on Climate Change models.
Researchers within and outside the study agree more data and research is needed to confirm or alter these results.
Most of us think of them as puffy and picturesque, but for climate modelers, clouds are a major thorn in the side, and are the hard question. Scientists do know clouds wield an outsize influence on climate: Reducing Earth’s cloud cover by just 5% would have the same planet-wide warming effect as all the CO2 released into the atmosphere since the start of the industrial age.
The big problem, however, is that as the earth warms, the effect of clouds changes too, and after decades of research and debate scientists can’t agree exactly how. Most think clouds will warm the earth overall, others think they could cool it, and no one is sure by how much either way.
Not knowing how these potentially huge cloud influences will unfold makes predicting climate change very difficult. The best estimate of temperature increase due to a doubling of atmospheric CO2 lies anywhere between +1.5C (2.7F) and +4.5C (8.1F), according to the U.N. Intergovernmental Panel on Climate Change (IPCC). Most of that gigantic uncertainty owes to the difficulty of modeling clouds.
Cumulonimbus cloud over Warsaw, Poland. Image by Kamil Nowacki.
Now that uncertainty range may have been narrowed down to a sliver, based on the findings of a new study by researchers at Imperial College, London. The team took a novel approach, sidestepping finicky cloud modeling schemes altogether, and turning to machine learning to predict climate “cloud feedback” instead.
Climate models work by slicing the world up into a three-dimensional grid and assigning values such as humidity, temperature, air pressure and a host of other descriptors within each entire cell. But clouds are wispy, ephemeral and driven by microscopic processes. “You can’t model the physics of clouds themselves,” says Paulo Ceppi, co-author of the new study. “If you think about a cloud, if you really wanted to simulate a cloud, you would need to simulate every individual droplet and ice crystal.”
Climate models divide the world into a vast three-dimensional grid with many individual cells — with each cell sometimes as much as 100 kilometers across. Average values for various factors in each cell are calculated, including humidity, temperature and air pressure. Clouds are difficult to model because their shape, size and composition are not easily fitted into, described and averaged within large cells. This diagram shows how individual clouds (top illustration) at various altitudes and which occupy only a portion of each cell, are averaged (bottom illustration) to show either the simple presence or absence of clouds filling an entire cells. Image produced by Studio Canek.
Clouds are also typically much smaller than the size of a single grid cell (with each cell usually covering 100km2, or 62 sq. mi.), making it hard to know where they fit into the model. And that is a huge problem, because where clouds are determines whether they cool or warm the earth.
Lower level clouds tend to reflect sunlight back out into space, having a cooling effect; higher level clouds can act as a blanket, trapping heat and warming the earth. At higher latitudes, where there is less sunlight to reflect, that blanketing effect currently dominates, all other factors being equal. Scientists think that clouds presently cool the earth more than they warm, but if low-level clouds decline or move further northward as global warming escalates, that could change.
High altitude cirrus clouds allow most of the sun’s shortwave radiation to pass through to the earth’s surface. Because they are cold, they trap much of the longwave radiation re-emitted upwards by the earth. Image by hehaden found on Flickr.
Puffy white stratocumulus clouds reflect most of the sun’s shortwave radiation back out into space, cooling the earth. Image courtesy of ISS Crew Earth Observations, Wikimedia Commons.
Traditionally, the cloud modeling problem has been addressed through “parameterization,” algorithms that predict the probability or percentage of cloudiness in a grid cell.
Initially, these algorithms were crude, sometimes just a binary choice between cloudy and not-cloudy depending on a cell’s relative humidity. Today’s algorithms are dense, knotty blocks of Fortran code, accounting for altitude, size, turbulence, amount of ice crystals, quantity and even chemistry of particles in the air.
Despite this added detail, or perhaps because of it, different parameterization schemes give wildly different results. Understanding why, says Ceppi, is difficult. Cloud models “are so complicated, and they have grown [more so] over generations of coders. People know what’s in there, but as soon as the model isn’t super simple, it becomes quite hard to describe what’s happening.”
Each cell “becomes a complex system, just like the real world,” says Peer Nowack, co-author of the new study.
Ceppi and Nowack took a different, simpler approach. Instead of trying to simulate the real world in ever finer detail, they looked at it from the top down. Reasoning that cloudiness at any given point statistically correlates to just a handful of key climate factors, chief among them surface temperature, they used a machine learning model to scan 20 years of climate data (from March 2000 to September 2019) — augmented by modeled estimates to fill in any gaps and seeking a formula that best defines the relationship of cloud changes to warming.
This wasn’t the first attempt to apply statistical analysis to clouds, but previous studies had focused only on certain types of clouds, or regions of the earth. The new study, by contrast, analyzed the entire planet, at every altitude. Moreover, instead of analyzing each point in isolation, the research team correlated the cloudiness at each point to a large area surrounding it, allowing the researchers to account for spatial patterns in cloud-forming factors.
Once the formulas had been derived, predictions could be made as to what might happen to clouds as global temperatures rise. The researchers then compared the predictions against the climate models used by the IPCC in drafting its assessment reports. Their results showed that the majority of climate modelers have it about right: global warming will result in a decline in low-level clouds and a rise in the altitude of high level clouds, implying a positive cloud feedback, meaning clouds will add to warming over time.
The results, says Ceppi, were “bang on” with the average effect seen in models.
“We find robust evidence that clouds amplify warming. Our results don’t shift the central [temperature increase] estimate one way or another… It’s not that things are worse than we previously thought. It’s that we’re more confident that it will be what we thought it would be [according to our current models].”
The researchers conclude that a doubling of atmospheric CO2 will most likely lead to a 3.2C (5.76F) global temperature increase, almost exactly in the middle of the IPCC’s estimate range. A temperature increase of less than 2C (3.6F) — the maximum increase to avoid climate disaster — has only a 0.5% probability, say the researchers.
“It’s an interesting study,” says Annica Ekman, a climate modeler at Stockholm University who was not involved in the research. She sees an important innovation in the use of spatial correlation. “That’s clever. I think we need that. I think this could be why previous parameterizations, when it was parameterizations… did not work so well, for low-level clouds, because they might not have had this large-scale influence in them.”
But machine learning is only as good as the data it is trained on, and is insufficient to make such a definitive conclusion in this case, says Kevin Trenberth, a Distinguished Scholar at the U.S. National Center for Atmospheric Research. “The data used [in the new study] are not real data, but come from models and are known to contain flaws,” he wrote in an email. Trenberth points out that the period under study was dominated by an unusually strong El Niño. “They would need another 50 years of data in order to sample a dozen El Nino events,” and confirm their results.
The study researchers maintain that they did account for data anomalies in their own uncertainty estimates, but admit more data would have been preferable.
Ceppi, however, anticipates a deeper concern. “The one limitation of our approach… would be if all the [cloud] models [used by the new study] happen to be wrong. And things are so non-linear, in a way that is not captured by any of the models. Then we fail.” But that will happen, he says, only at the highest levels of global warming.
“Then we’re talking about tipping points,” says Nowack. Then we’ve got bigger problems.
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Setting fire to the politics of global warming
There is a burning question at the centre of the latest Intergovernmental Panel on Climate Change report, the sixth assessment report into global warming (AR6). Is this a scientific document or a political one? The answer is that, by necessity, it is a bit of both.
Not too much should be read into the timing of the release of the report ahead of the Glasgow conference scheduled for November. This is because the Glasgow meeting was due to be held last year, before the report’s originally scheduled release in March.
Nonetheless, the report provides a rallying point for pressure groups, including the UN, to encourage world leaders to do more to reduce their nations’ greenhouse gas emissions.
From a scientific perspective, AR6 does not draw any startling new conclusions. Rather, scientists at the frontline of studying climate change are more convinced than ever that rising levels of carbon dioxide in the atmosphere have a direct relationship to rising surface temperatures averaged across the world. The science community is more willing to accept that natural variation can produce periods of negligible warming or even cooling.
The new learnings involve the use of climate models to provide a link between extreme weather events and a warming world. This remains a relatively new science and the results do not always have a high degree of confidence.
There is a robust defence of climate models overall but an admission that some newer models produce outcomes that cannot be accepted on their own.
Where the AR6 report becomes political is the extent to which it allows itself to become a vehicle for breathless prophecies of a looming Hadean future. This should not be surprising given that experts at the IPCC billed the report as “a code red for humanity”. In more sober tones, the report says warming since the start of the industrial revolution has been 1.07C and the best estimate of warming if greenhouse gases are allowed to double in the atmosphere is 3C.
It says the Paris Agreement’s more aspirational target to limit future warming to 1.5C will likely be exceeded on an annual basis in a little over a decade. Without action the actual Paris Agreement threshold of 2C will be breached in coming decades. But there is still a chance to meet even the lower target if the world can agree to decarbonise to net-zero emissions by 2050.
Unfortunately, the report has left itself open to the same criticisms that have dogged other recent appraisals of climate science. By necessity, the report includes a wide range of possible scenarios. Each scenario is based on a different trajectory for future greenhouse gas emissions. They range from sharp decreases in emissions to business as usual and a high-emissions scenario, RCP8.5.
The IPCC says, in general, no likelihood is attached to the scenarios assessed. But it does say the likelihood of high-emissions scenarios such as RCP8.5 is considered to be low. It is the high-emissions scenarios that have the greatest potential for bigger storms and tipping point extremes. Analysis shows the high-emissions scenarios that the IPCC says have a low probability dominate the report, with 41.5 per cent of all scenario mentions.
The scenarios judged most likely under current trends get less than half of this amount.
Many people no doubt will argue that even the best case scenarios can result in bad outcomes for the planet and that highlighting the negatives is necessary to get reluctant politicians to act. And they are probably right because as things stand it will take a minor miracle to break the logjam in global climate change politics that has frustrated progress throughout the IPCC’s existence and threatens to derail Boris Johnson’s Glasgow dream.
The issue is how to treat the developed and developing world differently but fairly and still cut total emissions. Scott Morrison touched on it on Tuesday when he said we could not ignore the fact the developing world accounted for two-thirds of global emissions and those emissions were rising.
The difficult part is that advanced economies have developed over a long time, principally on the basis of fossil fuel industries. And, as Morrison says, “It’s a very fair argument that the developing world makes, which says ‘why should our economic futures be denied when advanced economies around the world have been able to go forward on that basis of their energy economies over a long period of time?’ ”
This is the issue that has stalled global progress on limiting greenhouse gas emissions, which continue to grow as increases from developing economies swamp cuts from the developed world.
Out of total annual global emissions from fossil fuels of 36.4 billion tonnes, China emits 10.2 billion tonnes. The US is the next biggest emitter with 5.4 billion tonnes, then the EU with 2.9 billion, India 2.6 billion, Russia 2.4 billion and Japan 1.3 billion.
The developed world is proposing deep cuts to emissions but at the same time outsourcing industrial production of the things needed to make the transition to China, including the greenhouse gas emissions involved.
India forcefully has let it be known that it will continue to prioritise industrial development and poverty alleviation over curbing greenhouse gas emissions and is calling for a per capita measure.
Johnson has had high hopes of making the Glasgow summit the point at which the world turned its back on coal. But India and China refused even to attend a meeting called to discuss it.
The glue that is supposed to bring the sides together is money, with the transfer of funds from the developed to the developing world. But with coffers drained from tackling the Covid-19 pandemic the developed world is less well placed to deliver.
The situation is made more dire by growing pushback against governments in the EU and Britain, which are doing the most to make the change to net zero. Britain’s Committee on Climate Change, the agency charged with advising that a transition to net zero could be made at limited cost, has been ordered to produce its costings. It now says the spreadsheets of calculations have been deleted and overwritten.
In a statement on Monday, Johnson said we know what must be done to limit global warming. That is, “consign coal to history and shift to clean energy sources, protect nature and provide climate finance for countries on the front line”. Easier said than done.
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My other blogs. Main ones below
http://dissectleft.blogspot.com (DISSECTING LEFTISM )
http://edwatch.blogspot.com (EDUCATION WATCH)
http://pcwatch.blogspot.com (POLITICAL CORRECTNESS WATCH)
http://australian-politics.blogspot.com (AUSTRALIAN POLITICS)
http://snorphty.blogspot.com/ (TONGUE-TIED)
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Jim Hansen and his twin
1 comment:
We solved the clouds problem by ignoring them and making our models give the same results as the other models. /sarcasm
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