Dyer: Scientific word is out on coming ‘Hothouse Earth’

Christopher Davidson
August 13, 2018

The report, published this week in the Proceedings of the National Academy of Sciences of the US, states, "the Earth System may be approaching a planetary threshold that could lock in a continuing, rapid pathway towards much hotter conditions - Hothouse Earth". "Our study suggests that human-induced global warming of 2°C may trigger other Earth system processes, often called "feedbacks", that can drive further warming-even if we stop emitting greenhouse gases", says lead author Will Steffen from the Australian National University and Stockholm Resilience Centre.

The melting polar ice, increasing deforestation and rising greenhouse gases are indicators that the Earth is moving towards a unsafe hothouse state. In fact, it's the smaller part.

As Amazon rainforest is destroyed, Arctic permafrost thaws and Antarctic sea ice melts, these natural feedback mechanisms that now help store Earth's carbon will instead begin emitting it, scientists at the Swedish institute warned.

Now, this is not really news to climate scientists.

The authors of the study consider ten natural processes, some of which are "tipping elements" that lead to abrupt change if a critical threshold is crossed, turning from a "friend" storing carbon to a "foe" that emits it.

Yet the role of these feedbacks was not discussed in the scientific journals, not included in the predictions of future warming issued every four or five years by the Intergovernmental Panel on Climate Change (IPCC), and definitely not part of the public debate.

If you spot smoke billowing out of a house, you do not wait to see actual flames, check what substances are burning and calculate the heat of the fire. But that is not how science works.

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In contrast, employment fell in most goods-producing sectors, specifically manufacturing, construction and natural resources. Most of the new jobs went to women and were concentrated in three provinces: British Columbia, Ontario and Newfoundland.

So the climate scientists didn't make grand assertions - but they did manage to get the threshold of two degrees Celsius higher global temperature adopted as the never-exceed target for the IPCC's efforts to get the warming under control.

The United Nations has previously warned the voluntary greenhouse gas reductions agreed in Paris may not be enough to reach the 2 degrees target anyway.Even if governments kept to their pledges.

In the worst-case scenario, the researchers predict the Earth's climate would stabilise at around 4-5C higher - hotter than any point for 1.2 million years - and with sea level increase of up to 60m.

"Climate and other global changes show us that we humans are impacting the Earth system at the global level", says coauthor Katherine Richardson, professor at the Center for Macroecology, Evolution and Climate at the University of Copenhagen.

Maximising the chances of avoiding a "Hothouse Earth" requires not only reduction of carbon dioxide and other greenhouse gas emissions but also enhancement or creation of new biological carbon stores, the scientists warn, through improved forest, agricultural and soil management; biodiversity conservation; and technologies that remove carbon dioxide from the atmosphere and store it underground.

Geo-engineering ("solar radiation management") is already part of the package, and that it will be down to human beings to manage the entire ecosystem to keep it stable.

I haven't bothered to ask Lovelock if we are there yet.

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