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The latest generation of climate models is running hotter—here’s why
It largely comes down to their simulation of mid-latitude clouds.
Scott K. Johnson - 1/8/2020, 6:23 PM
Ahead of every Intergovernmental Panel on Climate Change (IPCC) report, the world’s climate modeling centers produce a central database of standardized simulations. Over the past year, an interesting trend has become apparent in the most recent round of this effort: the latest and greatest versions of these models are, on average, more sensitive to CO2, warming more in response to it than previous iterations. So what’s behind that behavior, and what does it tell us about the real world?
Climate sensitivity is one of the most-discussed numbers in climate science. Its most common formulation is the amount of warming that occurs when the concentration of CO2 in the atmosphere is doubled and the planet gets a century or two to come to a new equilibrium. It's an easy way to get a sense of what our emissions are likely to end up doing.
In climate models, this number is not chosen in advance; it emerges from all the physics and chemistry in the model. That means that as modeled processes are updated to improve their realism, the overall climate sensitivity of the model can change. As results have trickled in from the latest generation of models, their average climate sensitivity has noticeably increased. A new study led by Mark Zelinka of the Lawrence Livermore National Laboratory analyzes these new model simulations, comparing their behavior to the previous generation.
The analysis covered simulations from 19 of the 35 modeling groups, as not everything has come in yet. The climate sensitivity of these models spanned 1.8-5.6°C for doubled CO2, with an average of 3.9°C. The last generation fell into 2.1-4.7°C, with an average of 3.3°C. So there is a slight uptick in the sensitivity in the latest generation of models. (For context, the overall best estimate for real-world climate sensitivity has for decades been 1.5-4.5°C, centered on 3°C.)
Models work by dividing up the atmosphere into chunks called grid cells and then simulating atmospheric physics in each of these. To find out what caused the higher sensitivities, the researchers used a tool to break down the model responses in each grid cell. Their focus was on feedbacks—processes that either amplify or dampen warming. Differences in the various feedbacks are generally responsible for the range in overall sensitivity numbers.
In this analysis, most of the feedbacks have basically the same strength as in the previous generation of models. Low clouds, however, are behaving differently. That’s pretty important because low clouds can have a huge impact if they’re fluffy and reflective, shading the planet. If the amount of cloud shading changes as temperatures rise—which it does—you’ve got a feedback.
Low cloud behavior in models is a particularly lively topic of study. Previous research has found that, for example, models with the most realistic clouds (by some measure) tend to have higher climate sensitivities. And a lot of work goes into making new measurements of the physics and chemistry of clouds, with modelers then trying to make sure their simulations match that behavior.
In the new study, researchers found that the low cloud feedback in the new generation of models seems to have changed outside the tropics, particularly the mid-latitude Southern Hemisphere. The average feedback among the models is a little more positive, amplifying warming. That would mean that as the Earth warms, low cloud cover in this region is decreasing a bit and reflecting less sunlight back to space.
The researchers dug a little deeper to see what was behind this shift and found that it’s probably related to some changes in the cloud physics equations. Comparisons to satellite data had shown that models should allow more liquid droplets to remain liquid at cold temperatures, and at least some models have been tweaked accordingly. That could be enough to alter how much the clouds change as temperatures increase.
In short, the newer models don’t seem to be doing anything unrealistic to cause their higher sensitivities. But that doesn't necessarily mean they’re right. It’s going to take a lot more work to sift through these models and see which one has clouds that best match the real world. And as the Earth’s climate system is so interconnected, it’s even possible that some other factor—like a pattern of ocean temperature—is partly shaping cloud behavior.
Models aren’t the only way scientists estimate the Earth’s climate sensitivity. It’s also done by studying the historical record, for example, and past climate changes recorded by things like ice cores. Evaluating the new generation of climate models against those events might also provide some clarity.
This situation is certainly going to present a challenge for the authors of the upcoming IPCC report, though, as they’ll only be able to include studies published by September 2020. It’s a good bet that we’ll see more research on this topic in the coming months—and hopefully a lot of it, for the IPCC authors’ sake.
Geophysical Research Letters, 2020. DOI: 10.1029/2019GL085782 (About DOIs).
Climate emergency: 2019 was second hottest year on record
Last decade was also hottest yet in 150 years of measurements, say scientists
Damian Carrington Environment editor @dpcarrington Wed 15 Jan 2020 16.09 GMT
The year 2019 was the second hottest on record for the planet’s surface, according to latest research. The analyses reveal the scale of the climate crisis: both the past five years and the past decade are the hottest in 150 years.
The succession of records being broken year after year is “the drumbeat of the Anthropocene”, said one scientist, and is bringing increasingly severe storms, floods, droughts and wildfires.
The previous hottest year was in 2016, the year that a natural El Niño event boosted temperatures. The new data is for the average global surface air temperature. More than 90% of the heat trapped by human greenhouse gas emissions is absorbed by the oceans, but on Monday scientists revealed 2019 as the warmest yet recorded in the seas, calling it “dire news”.
The average temperature in 2019 was about 1.1C above the average from 1850-1900, before large-scale fossil fuel burning began. The world’s scientists have warned that global heating beyond 1.5C will significantly worsen extreme weather and suffering for hundreds of millions of people.
The World Economic Forum’s global risk assessment for the next decade, also published on Wednesday, found the top five dangers were all environmental, including extreme weather, failure to prepare for climate change and the destruction of the natural world.
“The last decade was easily the warmest decade in the record and is the first decade more than 1C above late 19th-century temperatures,” said Gavin Schmidt, of Nasa’s Goddard Institute for Space Studies, which produced one of the temperature records.
“What is important is the totality of evidence from multiple independent data sets that the Earth is warming, that human activity is driving it and the impacts are clearly being felt,” he said. “These announcements might sound like a broken record, but what is being heard is the drumbeat of the Anthropocene.”
“It’s now official that we have just completed the warmest decade on record, a reminder that the planet continues to warm as we continue to burn fossil fuels,” said Prof Michael Mann at Penn State University in the US.
While instrumental temperature records stretch back to 1850, data from ice cores indicate that today’s temperatures were last seen at least 100,000 years ago. Furthermore, the level of carbon dioxide is the highest it has been for several million years, when the sea level was 15-20 metres higher.
The four temperature datasets are compiled from many millions of surface temperature measurements taken across the globe, from all continents and all oceans. They are produced by the UK Met Office with the University of East Anglia (UEA), both Nasa and Noaa in the US, and Europe’s Copernicus Climate Change Service. Small differences between the analyses arise from how data-sparse polar regions are treated, but all agree that the past five years are the warmest five years since each global record began.
The Met Office’s forecast for global average temperature for 2020 suggests this year could well set another record and is very likely to be among the top three hottest. The UK government will host a critical UN climate summit in Glasgow in November. The UN secretary general, António Guterres, and many others are urging nations to increase dramatically their pledges to cut carbon emissions, which would lead to global temperatures rising by a disastrous 3-4C.
“It is obvious we are not succeeding in preventing dangerous anthropogenic interference with the climate system, which was the main goal of the original 1992 UN climate change convention,” said Bob Ward, of the Grantham Research Institute on Climate Change at the London School of Economics.
“Even if we succeed in limiting warming to 1.5C, this would not be a ‘safe’ level of warming for the world,” he said. “Therefore we must focus on cutting global emissions to net zero as soon as possible. We know the transition to a net zero economy is the growth story of the 21st century.”
Rosie Rogers, of Greenpeace UK, said: “We’re breaking more records than Usain Bolt, but there are no gold medals for dangerous temperature rises, or the floods and fires that come with it. We cannot run away from the climate emergency.”
Climate emergency: 2019 was second hottest year on record
Sounder » Thu Jan 16, 2020 1:24 pm wrote:Climate emergency: 2019 was second hottest year on record
And in other headline news: "Conspiracy Theorists" neutralized by a preference for fake shit over real shit; enabled by the fake shit.
coffin_dodger » Thu Jan 16, 2020 3:46 pm wrote:The funny thing is, I agree with everything that climate alarmists want actioned, but for different reasons than climate change. Cleaner air? Yes, please. Sustainable living? Yes, please. A slower, more reflective pace of life? Yes, please.
Climate change is as natural as water, wind, fire, growth and death. The climate has been changing since the dawn of this reality. The oceans rise and fall, the earth shifts beneath our feet, it becomes very warm and then very cold, across the centuries.
So why now? Why the alarmism over something that almost every single sentience on this world wholeheartedly agrees would improve the world for everyone, for their children?
Money. There's money to be made. We live in a financialised world. Everything has a monetary value. There's credits in it. Big business now. More for the emperors to shift across international bank accounts and into their own pockets. Money can turn the innocent into gluttons.
New sources of money generation are constantly required to prop up the monetary system. Climate alarmism fits the bill perfectly - based on an altruistic fundamental and open to uncritical abuse by the financial system.
And when the money dries up, the alarmism will abate. The air will remain dirty, the soil contaminated and the fires will rage hard. Our financialised system of doing things is the antithesis of sustainability, something we have yet to admit to ourselves.
It's also stupid
coffin_dodger » Thu Jan 16, 2020 8:50 pm wrote:Dr Evil said:It's also stupid
What is it with this board? Anyone who doesn't agree is stupid.
You're boring, not as brilliant as you think you are and I love the irony in that.
Climate emergency: 2019 was second hottest year on record
And in other headline news: "Conspiracy Theorists" neutralized by a preference for fake shit over real shit; enabled by the fake shit.
What the hell are you talking about? What's fake shit and what's real shit on your planet?
It’s a vision to transform the settlement patterns of Australia entrenched for more than 200 years. And all to be achieved by the private sector, with only minimal government involvement.
ASIC searches show a web of companies behind CLARA, and Cleary says there is a separate consortium agreement and “a number of firms that are funding us while we pass milestones”.
Until recently, there have been serious doubts that the project would even get off the ground, after being predicted to cost north of $100 billion to fully clear land and develop infrastructure.
Could there be something going on beneath the surface?
THE SMOKING GUN?
Cleary says they have secured crucial land to begin this mass project around the sites of the first two new cities, stating “we have some land in our control around those locations. It’s around those areas, about 10km from Shepparton.”
When investigating this, one must ask the question:
Is it merely a coincidence that this area is one of the locations under serious threat from fires? – http://greatershepparton.com.au/communi ... ncies/fire
This is not simply an isolated incident or ‘coincidence’.
Closer examination shows many of the current fires along the east coast correspond to the proposed route for the high-speed rail line and locations that are part of the CLARA proposal.
Let’s take a look below at the proposed smart city train line:
Now let’s take a look at the bushfire path across Australia:
Notice anything similar?
On further investigation, Shepparton is also revealed to be a region inside of CLARA’s documents explaining various locations the train line will run!
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