18/09/2020

Why Clouds Are The Missing Piece In The Climate Change Puzzle

The Conversation -  | 

Sam Schooler/Unsplash, CC BY-SA 

Authors
  •  is Lecturer in Climate Science, Imperial College London
  •  is Professor of Ocean Sciences, University of Liverpool     
How much our world will warm this century depends on the actions we take in coming decades. In order to keep global temperature rise below 1.5°C and avoid dangerous levels of warming, governments need to know how much carbon they can emit, and over what timeframe.

But current climate models don’t agree on where that threshold lies. In new research, we discovered one of the reasons why there is such a large range of estimates for how much carbon can be safely emitted: the uncertain behaviour of clouds. In some climate models, clouds strongly amplify warming. In others, they have a neutral effect or even dampen warming slightly. So why are clouds likely to play such a pivotal role in deciding our fate?

Projections by climate models typically reveal global temperatures rising almost in tandem with the total amount of carbon emitted over time. This is represented by the black line in the graph below. To avoid exceeding a certain level of warming, the world needs to limit how much carbon is emitted so that it remains within a certain carbon budget. In climate models where clouds amplify warming, this carbon budget is smaller (red dashed line and arrow). Where clouds have a near neutral or damping effect, the carbon budget is larger (blue dashed line and arrow).

Remaining carbon budgets in climate model projections

Paulo Ceppi, Author provided

Why are clouds so important?

Clouds can act like a parasol, cooling the Earth by reflecting sunlight away from the planet’s surface and back into space. But they can also act like an insulating blanket, warming the Earth by preventing some of the heat in our atmosphere from escaping into space as infrared radiation. This “blanket” effect is particularly noticeable during the winter, when cloudy nights are typically much warmer than cloud-free ones.

Which of these two effects dominates – parasol or blanket – depends on the altitude and thickness of the clouds. As a general rule, the higher a cloud is, the more effective it is at preventing heat from escaping into space. The thicker a cloud is, the better it is at reflecting sunlight away from Earth’s surface.

High, thin clouds let sunlight through while effectively preventing heat from escaping to space as infrared radiation, providing a net warming effect. Low, thick clouds strongly reflect sunlight, while having little impact on infrared radiation escaping to space, creating a net cooling effect.

As the atmosphere contains far more low, thick clouds than high, thin clouds, the parasol effect dominates and our planet would be much hotter if clouds did not exist.

Thin, high clouds tend to act as a parasol, while low, thick clouds act as a blanket. Paulo Ceppi, Author provided

The clouds are changing

Global warming is expected to cause changes in the amount of cloud cover, and the height and thickness of these clouds in the future, shifting the balance between the parasol and blanket effects of clouds. The knock-on effect this will have on temperature is known as cloud feedback. Climate change projections cannot ignore cloud feedback, as even relatively small changes in cloud properties can have significant implications for global temperature.

To predict how clouds will change in the future, our research combines evidence from observations and climate models with theoretical understanding of cloud physics. Taken together, this tells us that clouds are more likely to amplify global warming than they are to dampen it for two reasons.

First, the cover of low clouds is expected to decrease in the tropics as global temperatures rise, reducing their parasol effect. Second, it is well understood that high clouds will move into higher regions of the atmosphere as it warms, making them more effective blankets. These warming effects may be mitigated slightly by an increase in the thickness of clouds at high latitudes only, particularly over the Southern Ocean around Antarctica, but this will not cancel out the overall warming effect.

While we do know that clouds will likely amplify global warming, there is still a great deal of uncertainty about how strong this effect will be. Here climate models are of little help, as they can only simulate the bulk properties of the atmosphere over scales of tens of kilometres and several hours. Tiny cloud droplets form and evaporate in minutes. Models miss these small-scale details, but they’re needed for accurate predictions.

Climate models have to resort to simplifications in order to represent clouds, which introduces error. As different models make different simplifications in their portrayal of cloud processes, they also make different predictions of the cloud feedback, which results in a range of global warming projections and differences in our remaining carbon budget. For a given future carbon emissions scenario, clouds are the single most important factor behind the differences in future warming predicted between models.

Should we be worried?

Climate sensitivity, the amount of long-term global warming expected if we double the amount of carbon in the atmosphere, is currently estimated to lie between 1.5° and 4.5°C. This consequences of this level of warming are already disturbing, but several new climate models currently being developed by world-leading researchers are projecting warming in excess of 5°C. These new models also feature an improved representation of cloud processes, so this seems to suggest that global warming could be even worse than we thought.

Thankfully, there are alternative projections that point towards more moderate warming. The same models with the highest long-term warming also overestimated warming trends that have already been observed. In the meantime, further research efforts are underway to pin down the role of clouds in climate sensitivity.

It is clear that our planet will continue to warm as we carry on emitting carbon into the atmosphere. But by how much will remain written in the clouds.

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(AU) ‘A Dose Of Reality’: Morrison Government’s New $1.9 Billion Techno-Fix For Climate Change Is A Small Step

The Conversation - 

Dean Lewins/AAP 

Author
 is Director, Centre for Climate and Energy Policy, Australian National University     
The Morrison government today announced A$1.9 billion over ten years to develop clean technology in industry, agriculture and transport. 

 In some ways it’s a step in the right direction, but a far cry from what’s needed to drive Australia’s shift to a low emissions economy.

The big change involves what the money is for. The new funding will enable the Australian Renewable Energy Agency (ARENA) to support technologies such as green steel production, industrial processes to reduce energy consumption and somewhat controversially, carbon-capture and storage and soil-carbon sequestration.

This is a big move away from ARENA’s current investment priorities. Importantly it means ARENA will continue to operate, as it is running out of money now.

However technology development alone is not enough to cut Australia’s emissions deeply and quickly – which is what’s needed to address the climate threat. Other policies and more money will be needed.

Cutting emissions from industry will be a focus of the new spending. Dean Lewins/AAPNew role for ARENA

ARENA will receive the lion’s share of the money: A$1.4 billion over ten years in guaranteed baseline funding. ARENA has spent A$1.6 billion since it was established in 2012. So the new funding is lower on an annual basis. It’s also far less than what’s needed to properly meet the challenge, in a country with a large industrial sector and huge opportunities for zero carbon production.

To date, ARENA’s investments have focused on renewable energy supply. Prime Minister Scott Morrison today said the renewables industry was enjoying a “world-leading boom” and no longer needs government subsidies.

Critics may be dismayed to see ARENA steered away from its original purpose. But it is true solar parks and wind farms are now commercially viable, and technologies to integrate large amounts of renewables into the grid are available.

So it makes sense to spend new research and development (R&D) funding on the next generation of low-emissions technologies. But how to choose what to spend the money on?

The prime minister says renewable energy no longer needs subsidies. AAP Image/Mick Tsikas

A few simple principles should inform those choices. The spending should help develop new zero- or low-emissions technologies or make them cheaper. It should also enable the shift to a net-zero emissions future, rather than locking in structures that continue to emit. The investment choices should be made by independent bodies such as ARENA’s board, based on research and expert judgement, rather than politically determined priorities.

For the industrial sector, the case for supporting zero-emissions technologies is clear. A sizeable share of Australia’s total emissions stem from fossil fuel use in industry.

In some cases, government-supported R&D could help lay the foundation for zero-emissions industries of the future. But in others, what’s needed is a financial incentive for businesses to switch to clean energy or zero-emissions production methods, or regulation to require cleaner processes.

Green steel is a perfect example of the positive change that is possible. Steel can be made using clean hydrogen and renewable electricity, and the long term possibility of a green steel industry in Australia is tantalising.

Steel could be made cleanly using hydrogen instead of coking coal. Dean Lewins/AAP

A future for fossil fuels?

The government’s support for carbon capture and storage (CCS) will be highly contested, because it’s a way to continue using fossil fuels at reduced – though not zero – emissions. This is achieved by capturing carbon dioxide before it enters the atmosphere and storing it underground, a technically feasible but costly process.

CCS will not perpetuate fossil fuel use in the energy sector, because renewables combined with energy storage are now much cheaper. Rather, CCS can be an option in specific processes that do not have ready alternatives, such as the production of cement, chemicals and fertiliser.

One step further is so-called “carbon capture and use” (CCU), where carbon dioxide is not pumped underground but turned into products, such as building materials. One program announced is for pilot projects of that kind.

A different proposition is the idea of hydrogen produced from coal or gas, in which some resulting emissions are captured. This method competes with “green” hydrogen produced using renewable electricity. It seems the government for now intends to support fossil fuel-derived hydrogen.

Reducing fossil fuel use, and using CCS/CCU where it makes sense, will not get the world to net-zero emissions. Emissions from other sources must be cut by as much as technically possible, at justifiable cost. Remaining emissions must then be negated by drawing carbon dioxide from the atmosphere. Such “negative emissions” can be achieved through technological means, and also by permanently increasing the amount of carbon stored in plants and soil.

The new funding includes support for increasing the amount of soil carbon. This method may hold promise in principle, but in practice its effectiveness is uncertain, and hard to measure. At the same time, the large emissions from agriculture are not yet addressed.

Reducing the burning of fossil fuels is not enough to get to net-zero emissions. Matt Black Productions

A piecemeal effort

The spending amounts to A$140 million per year for ARENA, plus about A$500 million all up through other programs. A dose of reality is needed about what this money can achieve. It will create better understanding of options, some technological progress across the board and surely the occasional highlight. But a much greater effort is likely needed to achieve fundamental technological breakthroughs. And crucially, new technologies must be widely deployed.

For a sense of scale, consider that the Snowy 2.0 scheme is costed at around A$5 billion, and a single 1 gigawatt gas power plant, as mooted by the government for the Hunter Valley, would cost in the order of A$1.5 billion to build.

As well as additional spending, policies will be needed to drive the uptake of low-emissions technologies. The shift to renewables is now happening in the energy sector without government help, though some hurdles remain. But we cannot expect the same across the economy.

Governments will need to help drive uptake through policy. The most efficient way is usually to ensure producers of emissions pay for the environmental damage caused. In other words, putting a price on carbon.

The funding announced today is merely one piece of a national long-term strategy to deeply cut emissions – and not a particularly big piece.

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Antarctica’s ‘Doomsday Glacier’ Is Starting To Crack

EcoWatch - Olivia Rosane

Antarctica's Thwaites Glacier, aka the "Doomsday Glacier," is starting to crack. NASA / Wikimedia Commons

Antarctica's Thwaites Glacier has been called the "Doomsday Glacier."

Thwaites and its neighbor, the Pine Island Glacier, are among those in West Antarctica most influenced by the climate crisis.

If they melted, they could destabilize the entire West Antarctic Ice Sheet, which has the potential to contribute about 10 feet to global sea level rise.

Now, a new study has found that the ice shelves supporting the two crucial glaciers are beginning to fissure and crack.

"These ice shelves are in the early phase of disintegration," study leader and Delft University of Technology satellite expert Stef Lhermitte told CNN. "They're starting to tear apart."

The research, published in the Proceedings of the National Academy of Sciences Monday, looked at satellite images taken between 1997 and 2019 to document the ice shelves' increasing damage. The images show crevices and fissures in the glaciers, according to a Delft press release.


Ice shelves are important for a glacier's stability because they provide support, similarly to how flying buttresses support a cathedral, International Thwaites Glacier Collaboration lead principle researcher Brent Goehring told ABC News. Goehring was not involved with the paper.

The damage is occurring in the glaciers' shear zones, parts of the ice shelves where the fast-moving ice on top connects with the slower-moving ice or rock beneath, CNN explained. That damage significantly increased in 2016.

The researchers think that the damage they observed to the ice shelves will only beget more damage, Lhermitte explained in a Twitter thread. This is for three reasons:
  1. The damage undermines the structural integrity of the ice shelves.
  2. The damage weakens the ice shelves and makes them more vulnerable to warming air and ocean temperatures.
  3. The damage creates a feedback loop, leading to more weakening and more damage.
Because of this, the scientists suggested that the damage be accounted for in climate models to better predict how Antarctic ice melt will contribute to sea level rise.

Sea levels are currently rising by around 3.5 millimeters a year, and the Thwaites Glacier accounts for four to five percent of that, Goehring told ABC News.

"If those glaciers would destabilize, a lot of neighboring areas would also fall apart, causing a widespread collapse," Indrani Das, a co-principle researcher on an International Thwaites Glacier Collaboration project, told ABC News. "It would cause a huge sea level rise."

However, Das did not think it likely that the collapse would take place this century.

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