Why Limit Global Warming to 2°C and Not More?

The international community has set a target of limiting global warming to 2°C compared to pre-industrial levels in order to avoid the most serious effects of climate change. This 2°C threshold was established due to the magnitude of the potential consequences that could result from higher warming.

global warming climate change

Proposing a target to restrict global warming to a maximum of +2°C by 2050, relative to the 1990 benchmark, is rooted in historical context dating back over 100,000 years. During that distant period, the Earth experienced a comparable average temperature without undergoing any significant climatic disasters. This historical precedent suggests the potential validity of applying the same principle in the present era.

However, it’s important to acknowledge that climate patterns exhibit non-linear behavior and encompass critical thresholds. Therefore, absolute assurance cannot be provided that surpassing a 2°C rise in average temperature won’t trigger an uncontrollable climatic escalation.

Positive Climate Feedback

Feedback loop: warming leads to more CO2, which causes more warming
Feedback loop: warming leads to more CO2, which causes more warming. Image: Climate Atlas.

Once the temperature surpasses the 2°C threshold, there emerges a heightened potential for setting in motion positive feedback loops. A case in point is the liberation of methane due to the thawing of permafrost, a phenomenon that possesses the capacity to expedite the process of warming.

In fact, the current climate system operates with intricacies like carbon sinks and albedo, which can lead to abrupt transformations under specific combinations of temperature and humidity. These transformations have the potential to inflict severe harm on ecosystems and societies. Additionally, the surge in methane emissions, a greenhouse gas that possesses 25 times more potency than CO2, is another concerning consequence. This surge is instigated by the thawing of permafrost and the release of methane clathrates into the atmosphere.

Beyond 2°C of Warming

Prudence dictates our adherence to the 2°C threshold, though it is not without flexibility. Yet, as we deviate more from this standard, the potential for significant repercussions looms larger.

Ecosystem Tipping Points

Greenland ice sheet (east coast, view from plane)
Aerial view of Greenland Ice Sheet or Inland Ice as it covers 80% of Greenland.

Certain areas might surpass crucial thresholds, leading to irreversible impacts on ecosystems. For instance, the disappearance of the Greenland ice sheet could be triggered by warming beyond 2°C.

Following the conclusion of COP21, the Paris Accord considered a cap of +1.5°C to be attainable. However, after a span of two years, achieving this target seems elusive. Unless nations intensify their endeavors to curtail greenhouse gas emissions within the upcoming decade, there is a considerable possibility of a temperature surge of +4°C by the turn of the century.

Commitment to Future Emissions

The objective of the 2°C goal is to limit the release of greenhouse gases in a manner that prevents the occurrence of uncontrollable heating patterns. As the temperature rises beyond this particular limit, the task of maintaining stable levels of greenhouse gases within the atmosphere grows progressively more demanding.

Above +2°C, we start to move away from the current climate system, and at +4°C, we enter an unknown model. At +3°C, climate change will not be linear; there will be local and abrupt effects.