Harri Tiido: Will the climate stop supporting human existence?
This time, the background discussion focus on climate change. Scientists say that we are closer than expected to a so‑called point of no return, after which global warming becomes uncontrollable, notes Harri Tiido.
From time to time I have brought up environmental topics to remind us that the extreme weather events we hear about in the news are not something merely temporary. One could argue that the weather has always changed now and then, but scientists who monitor conditions have their own view — namely, that this is largely a one‑directional trend.
Given Estonia's winter this year, talk of global warming might sound exaggerated, but weather must be seen in a global context. The extreme conditions we see now, for instance in Western Europe, may point to even more difficult conditions in the future.
The journal One Earth published a study discussing a possible trajectory toward a so‑called "Hothouse Earth." This threat was already discussed in 2018, and scientists have refined the picture over time. The article addresses the possible impact of recent scientific discoveries on climate feedbacks and identifies 16 so‑called tipping points. These include, among others, the Greenland and Antarctic ice sheets, mountain glaciers, boreal forests and permafrost, the Amazon rainforest, and the Atlantic circulation system — all of which influence the global climate.
A tipping point may already have been reached in Greenland and West Antarctica. Permafrost, mountain glaciers, and the Amazon rainforest appear to be on the brink. And all these processes are interconnected. One shortcoming in how climate issues are often discussed is the tendency to treat different phenomena separately — even though they are linked, and reaching a tipping point in one area can trigger a domino effect across the planet.
The Atlantic circulation system is already showing signs of weakening, influenced by meltwater from Greenland and Antarctica entering the oceans. In turn, this weakening alters atmospheric circulation, shifting tropical rainfall belts and drying parts of the Amazon region, affecting its capacity to absorb carbon and its biodiversity. Carbon released from the Amazon further intensifies global warming, and together with other drivers, this sets off a cascade of interconnected tipping points.
From there, development could move toward a greenhouse‑type climate, and at some point the process becomes self‑reinforcing — meaning that even later reductions in carbon dioxide emissions would no longer be enough to stop it.
Looking at longer timescales, during the mid‑ and late Pleistocene (about 1.2 million to 11,700 years ago), the climate fluctuated between ice ages and warmer periods, with temperatures ranging from –6°C to +2°C relative to the pre‑industrial average of about 14°C.
The Holocene, which began about 11,700 years ago, was a period of relatively stable weather, allowing agriculture, organized societies, and modern ecosystems to develop. Today, average temperatures are as high as — or higher than — at any point in the last 125,000 years. Carbon dioxide levels are likely higher now than at any time in the past two million years.
Several elements of our climate system appear to be closer to destabilization than previously thought. The Paris Agreement set a limit of 1.5°C above the pre‑industrial average, yet this threshold was recently exceeded for 12 consecutive months, accompanied by record heatwaves, wildfires, floods, and other extremes.
Climate models still cannot fully capture the system's complexity. They did not predict that the 1.5°C threshold would be exceeded in 2024. And warming appears to be accelerating: whereas in the mid‑20th century temperatures rose on average by 0.05°C per decade, the current increase is about 0.31°C per decade — six times higher.
According to scientists, we are closer than expected to a point of irreversibility, after which global warming becomes uncontrollable. This would lock the world into a new and hellish "greenhouse climate," far worse than the currently projected 2–3°C rise. The climate would then differ greatly from that of the past 11,000 years, which enabled human civilization to develop. With a 3–4°C increase, scientists predict that economies and societies would no longer function as they do today — but the arrival of a greenhouse climate would be even worse.
Predicting weather developments is complex and constantly evolving, depending on how ongoing changes are recorded. Between 2023 and 2025, when temperatures began exceeding the 1.5°C target, 80% of the world's coral reefs experienced bleaching — the largest coral‑damaging event in recorded history. Coral loss could lead to poverty, migration, and economic shocks. Coral reefs provide more benefits to humanity per unit than any other ecosystem. In economic terms, their value is estimated at around $10 trillion per year.
We have already discussed the impact of disruptions to the Atlantic circulation system. To recall, if the system reaches a tipping point, much of southwestern Europe could become less habitable. This would also have devastating effects on sectors such as real estate — after all, who would want to buy property in areas that may soon be underwater? And so on — there's little point repeating all these dire scenarios.
Scientists also point to positive climate tipping points. These involve changes in social, technological, and ecological systems that could steer humanity toward a more sustainable path. Such points can emerge from self‑reinforcing dynamics.
For example, the more people adopt certain behaviors, the greater the influence on others to follow. In technology, wider adoption leads to improvements and lower costs, while also encouraging the development of new technologies.
Take solar panels, wind turbines, and better batteries — all have become more efficient and cheaper over time. And three‑quarters of the world's population support stronger climate policy. Unfortunately, more problems arise from governments and populist movements, which have made opposition to climate policy one of their key agendas.
Further reading
Editor: Kaupo Meiel, Argo Ideon
