A recent publication in Proceedings of the National Academy of Sciences indicates that global temperatures rising over 2 degrees Celsius will trigger self-reinforcing feedback processes, potentially tipping Earth into "Hothouse" conditions that would result in mass extinctions as well as inhospitable environments unsuitable for human life.
How Hothouse Earth Could Make Life Impossible for Humans and Nature
Even after decades of environmental action and legislation, investments in renewable energy, electric cars and 29 climate conferences - carbon emissions continue to rise and we're on our way towards Hothouse Earth; an ecological catastrophe which could cause mass extinctions as temperatures increase up to 10 degrees above current values.
Scientists conducting this study, published in US Proceedings of the National Academy of Sciences, examined 10 naturally occurring "feedbacks," or tipping elements, that can cause sudden change if they cross certain thresholds. Once set into motion, these feedbacks act like dominoes that push closer towards Hothouse Earth - but once that tipping point has been crossed it's impossible to reverse.
If we enter into a Hothouse Earth scenario, rivers could flood deltaic environments and storms could devastate coastal cities before coral reefs have even had time to form--all by the end of this century or possibly sooner. Melting polar ice caps will eventually cause sea levels to rise dramatically and flood land that's home to hundreds of millions of people worldwide posing serious risks to human health, economies and political stability around the world.
Scientists do not offer an estimate for how likely we are to cross a climate threshold, although media articles often assert that 2 degrees Celsius marks "point of no return". Although this threshold remains uncertain, understanding its possible path towards Hothouse Earth can help us take measures necessary to avoid it.
Avoiding a Hothouse Earth will require not just cutting greenhouse gas emissions, but also increasing soil carbon storage and biodiversity, and developing technologies to extract carbon dioxide from the atmosphere. Furthermore, it's crucial to realize that climate change is just one part of an interrelated set of crises such as water shortages, food insecurity and biodiversity loss - for which only lifestyle, economic and societal alterations will provide lasting solutions; this is what planetary stewardship means.
The Looming Threat of Irreversible Climate Change and Mass Extinction
At present, climate change is happening at an uncontrollable rate that far outstrips scientists' worst predictions, and many changes are irreversible. According to the Intergovernmental Panel on Climate Change (IPCC), human-caused warming above 2 degrees Celsius could trigger irreparable global catastrophe via "tipping cascades."
A greenhouse provides protection for plants against cold conditions; hothouses provide additional artificial sources of heat as well as sunlight. Both terms are often used interchangeably to refer to nurseries or enclosed gardens where plants are grown for sale or display; greenhouses have increasingly become essential in protecting crops from harsh environmental conditions like droughts and floods that would otherwise threaten them.
Many people view climate change as an obligation from the Industrial Revolution that must now be paid back; this approach can be useful, yet overlooks the fact that we are currently adding carbon to the atmosphere at rates far greater than ever seen before in Earth history.
Extra carbon emissions are contributing to warming and acidification of oceans, decreasing biodiversity, harming people and wildlife and increasing climate change risks that threaten not only irreversibility but also mass extinction events that threaten human civilization itself.
Climate change is already creating havoc in nature and endangering millions of people, particularly in low-lying areas and other vulnerable communities. Governments must prioritize risk reduction strategies that include climate change in terms of sustainable development, social inclusion and ecosystem services.
IPCC's latest report warns that, to avoid catastrophic global warming, greenhouse gas emissions must be cut by roughly one third from current levels by 2030. To achieve this goal, all sectors of society -- governments, businesses, communities and individuals alike -- will have to work collaboratively together so risks and opportunities are assessed, prioritized and addressed immediately.
The IPCC Special Report on 1.5 Degree Celsius provides an in-depth overview of climate change and its impacts. Additionally, this report presents options on how we can increase nature and human resilience against climate change.
The Perils of Hothouse Earth
Many are fearful of the concept of a Hothouse Earth, especially when presented as an irreversible process. Unfortunately, many articles on the subject give this impression; furthermore they tend to suggest that 2 degrees Celsius warming threshold will trigger feedbacks which further raise temperature through domino effects and create further environmental havoc.
These headlines may be misleading and exaggerated, yet remain commonplace. They give the false impression that crossing the climate threshold is inevitable unless we immediately cut carbon emissions and improve energy efficiency; but these reports fail to mention important details like many feedback processes described in a research paper that identified Hothouse Earth pathways may occur more rapidly than expected unless we take measures to stop them.
In their PNAS study, scientists identified 10 feedback processes that could trigger uncontrollable releases of carbon back into the atmosphere even after we have reduced emissions. They included permafrost thaw, accelerated deforestation and disappearance of Arctic and Antarctic sea ice and glaciers - events they warned might happen within several decades but did not specify.
Other natural systems, like oceans, may also trigger uncontrollable feedback loops with potentially more profound repercussions than those caused by human emissions alone. Such actions could bring about global warming, aridification and acidification which would make earth inhabitable for human and other species alike.
Scientists have recently found evidence of such a scenario in Earth history. Around 100 million years ago, conditions similar to our current ones -- high carbon dioxide levels and warm global climate -- led to relatively peaceful coexistence among diverse life forms from both land and sea environments.
Though these conditions did not last long, they provided a warning that human civilization may very quickly render Earth inhospitable to most living things and render humans obsolete as we head down our current path of decarbonizing the global economy, improving agriculture practices, reducing deforestation rates and developing carbon capture technologies. Our best hope now is to reduce carbon emissions worldwide through decarbonization efforts such as decarbonizing world economies and agriculture, improving yields from existing fields, reducing deforestation rates and developing carbon capture technology solutions.
Why We Need to Avoid Crossing the Climate Threshold
Scientists have long agreed that global warming exceeding 2 degrees Celsius above pre-industrial levels would be catastrophic, making this number the primary target of international diplomacy and negotiations.
Crossing this threshold won't simply bring hotter days; rather, crossing this mark will unleash global destruction by activating environmental feedback loops that cause unprecedented extreme weather events and major climate disruptions across the planet.
At such temperatures, some of the world's most densely populated cities could experience extended heat stress due to limited sweat production - leading to widespread illness and even death among inhabitants - ultimately endangering both humans and much of nature alike.
Other effects include the extinction of many species, biodiversity loss and severe food and water shortages. Furthermore, an increasingly hotter Earth will make living more hazardous for vulnerable populations like elderly people and children.
Already we can witness some of these threats first-hand, such as sea-level rises threatening coastal communities and pushing them inland. That is why it is critical that nations continue their efforts towards meeting the Paris agreement goals as soon as possible.
Remembering this fact, we need to show people why preventing climate change will benefit everyone involved, including themselves and their communities. Therefore, explaining how avoiding crossing 1.5degC mark will benefit not just humanity as a whole but specifically them and their family too will be vital in engaging people effectively with climate action.
A hothouse is a heated glass structure used to cultivate plants and flowers for harvest. But the word also applies to situations or environments which are highly intense, particularly ones characterized by intellectual or emotional activity; such as those created at sporting events when large crowds create an intense environment where emotions may run high.
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