Nav: Home

Earth at risk of heading towards 'hothouse Earth' state

August 06, 2018

Keeping global warming to within 1.5-2°C may be more difficult than previously assessed, according to researchers.

An international team of scientists has published a study in Proceedings of the National Academy of Sciences (PNAS) showing that even if the carbon emission reductions called for in the Paris Agreement are met, there is a risk of Earth entering what the scientists call "Hothouse Earth" conditions. A "Hothouse Earth" climate will in the long-term stabilize at a global average of 4-5°C higher than pre-industrial temperatures with sea level 10-60 m higher than today, the paper says. The authors conclude it is now urgent to greatly accelerate the transition towards an emission-free world economy.

"Human emissions of greenhouse gas are not the sole determinant of temperature on 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. "Avoiding this scenario requires a redirection of human actions from exploitation to stewardship of the Earth system."

Currently, global average temperatures are just over 1°C above pre-industrial and rising at 0.17°C per decade.

The authors of the study consider ten natural feedback processes, some of which are "tipping elements" that lead to abrupt change if a critical threshold is crossed. These feedbacks could turn from being a "friend" that stores carbon to a "foe" that emits it uncontrollably in a warmer world. These feedbacks are: permafrost thaw, loss of methane hydrates from the ocean floor, weakening land and ocean carbon sinks, increasing bacterial respiration in the oceans, Amazon rainforest dieback, boreal forest dieback, reduction of northern hemisphere snow cover, loss of Arctic summer sea ice, and reduction of Antarctic sea ice and polar ice sheets.

"These tipping elements can potentially act like a row of dominoes. Once one is pushed over, it pushes Earth towards another. It may be very difficult or impossible to stop the whole row of dominoes from tumbling over. Places on Earth will become uninhabitable if "Hothouse Earth" becomes the reality," adds co-author Johan Rockström, Executive Director of the Stockholm Resilience Centre and incoming co-Director of the Potsdam Institute for Climate Impact Research.

Hans Joachim Schellnhuber, Director of the Potsdam Institute for Climate Impact Research, says, "We show how industrial-age greenhouse gas emissions force our climate, and ultimately the Earth system, out of balance. In particular, we address tipping elements in the planetary machinery that might, once a certain stress level has been passed, one by one change fundamentally, rapidly, and perhaps irreversibly. This cascade of events may tip the entire Earth system into a new mode of operation."

"What we do not know yet is whether the climate system can be safely 'parked' near 2°C above preindustrial levels, as the Paris Agreement envisages. Or if it will, once pushed so far, slip down the slope towards a hothouse planet. Research must assess this risk as soon as possible."

Cutting greenhouse gases is not enough

Maximizing the chances of avoiding a "Hothouse Earth" requires not only reduction of carbon dioxide and other greenhouse gas emissions but also enhancement and/or creation of new biological carbon stores, for example, through improved forest, agricultural and soil management; biodiversity conservation; and technologies that remove carbon dioxide from the atmosphere and store it underground, the paper says. Critically, the study emphasizes that these measures must be underpinned by fundamental societal changes that are required to maintain a "Stabilized Earth" where temperatures are ~2°C warmer that the pre-industrial.

"Climate and other global changes show us that we humans are impacting the Earth system at the global level. This means that we as a global community can also manage our relationship with the system to influence future planetary conditions. This study identifies some of the levers that can be used to do so," concludes co-author, Katherine Richardson from the University of Copenhagen.
-end-
Contact persons

Authors

Will Steffen
Australian National University and Stockholm Resilience Centre
e-mail: Will.Steffen@anu.edu.au
Phone: +61-447-980-495;

Johan Rockström
Executive director of the Stockholm Resilience Centre
e-mail: owen.gaffney@su.se
Phone: +46 (0) 734604833

Katherine Richardson
Leader, Sustainablity Science Centre, University of Copenhagen
e-mail: kari@science.ku.dk
Phone: +45 28754285

Media contacts

Stockholm Resilience Centre

Owen Gaffney
Owen.gaffney@su.se
Phone: +46 (0) 734604833

Potsdam Institute for Climate Impact Research

press@pik-potsdam.de
Phone: +49 331 288 25 07

University of Copenhagen

Lotte Jensen
lotte.jensen@snm.ku.dk

Australia

jo.meehan@anu.edu.au
alexia@climatecouncil.org.au

Stockholm Resilience Centre

Related Greenhouse Gas Articles:

Models, observations not so far apart on planet's response to greenhouse gas emissions
Recent observations suggest less long-term warming, or climate sensitivity, than the predicted by climate models.
Gas hydrate breakdown unlikely to cause massive greenhouse gas release
A recent interpretive review of scientific literature performed by the US Geological Survey and the University of Rochester sheds light on the interactions of gas hydrates and climate.
New Marcellus development boom will triple greenhouse gas emissions from PA's natural gas
Natural gas production on Pennsylvania's vast black shale deposit known as the Marcellus Shale will nearly double by 2030 to meet growing demand, tripling Pennsylvania's greenhouse gas emissions from the natural gas sector relative to 2012 levels, according to a report published today by Delaware Riverkeeper Network.
UCI scientists identify a new approach to recycle greenhouse gas
Using a novel approach involving a key enzyme that helps regulate global nitrogen, University of California, Irvine molecular biologists have discovered an effective way to convert carbon dioxide (CO2) to carbon monoxide (CO) that can be adapted for commercial applications like biofuel synthesis.
Bacterial mechanism converts nitrogen to greenhouse gas
Cornell University researchers have discovered a biological mechanism that helps convert nitrogen-based fertilizer into nitrous oxide, an ozone-depleting greenhouse gas.
Drying Arctic soils could accelerate greenhouse gas emissions
A new study published in Nature Climate Change indicates soil moisture levels will determine how much carbon is released to the atmosphere as rising temperatures thaw Arctic lands.
'Watchdog' for greenhouse gas emissions
Mistakes can happen when estimating emissions of greenhouse gases such as carbon dioxide and methane.
Greenhouse gas mitigation potential from livestock sector revealed
Scientists have found that the global livestock sector can maintain the economic and social benefits it delivers while significantly reducing emissions, and in doing so help meet the global mitigation challenge.
Greenhouse gas 'bookkeeping' turned on its head
For the first time scientists have looked at the net balance of the three major greenhouse gases -- carbon dioxide, methane, and nitrous oxide -- for every region of Earth's landmasses.
Soil frost affects greenhouse gas emissions in the Arctic
Soil frost is a nearly universal process in the Arctic.

Related Greenhouse Gas Reading:

Best Science Podcasts 2019

We have hand picked the best science podcasts for 2019. Sit back and enjoy new science podcasts updated daily from your favorite science news services and scientists.
Now Playing: TED Radio Hour

Jumpstarting Creativity
Our greatest breakthroughs and triumphs have one thing in common: creativity. But how do you ignite it? And how do you rekindle it? This hour, TED speakers explore ideas on jumpstarting creativity. Guests include economist Tim Harford, producer Helen Marriage, artificial intelligence researcher Steve Engels, and behavioral scientist Marily Oppezzo.
Now Playing: Science for the People

#524 The Human Network
What does a network of humans look like and how does it work? How does information spread? How do decisions and opinions spread? What gets distorted as it moves through the network and why? This week we dig into the ins and outs of human networks with Matthew Jackson, Professor of Economics at Stanford University and author of the book "The Human Network: How Your Social Position Determines Your Power, Beliefs, and Behaviours".