How 0.5°C can mean the difference between life and death

You have likely heard of the 1.5°C limit for global warming. Perhaps you are even familiar with the saying: “1.5 to stay alive.” But do you know where this saying came from or why such a seemingly small and arbitrary number was chosen to be our goal not to surpass? And what happens if we do surpass 1.5°C of warming? And how likely is that to happen? In order to answer these questions, one must examine a combination of scientific studies, data sets, public policy agreements, and historical happenings. This blogpost will do just that. The story of the introduction of the 1.5°C limit is a tale of triumph for the underdogs, while the story of what will happen if we don’t limit warming to 1.5°C (and we probably won’t) fits more into the apocalyptic genre. 

Introduction to the 1.5°C limit

The 1.5°C limit for global warming is part of the Paris agreement and was established at the United Nations COP21 (21st Conference of the Parties) in Paris in December 2015. The Paris agreement is a legally binding international treaty that instructs nations to “limit global warming to well below 2, preferably to 1.5 degrees Celsius, compared to pre-industrial levels.” These so-called “pre-industrial levels” are based on temperatures recorded between 1850 and 1900. As part of the agreement, nations must begin to implement changes in their infrastructure that significantly reduce their carbon emissions. In addition to initiating infrastructure changes, these nations are encouraged to create long-term plans which describe how they will keep warming below 1.5°C. In addition to this, wealthier countries are encouraged to provide financial and technological support for climate mitigation to countries that require it.

Before the Paris agreement, the only official goal for limiting global warming was placed at 2°C. However, in the years leading up to the Paris agreement, public support for a 1.5°C limit had been rising, with the smallest, most vulnerable countries on the front lines of this campaign.

This is a timeline from the IPCC report showing the history of how the 1.5 degree limit came to be.

How the 1.5°C limit came to be

“How can you ask my country to go extinct” were the words that echoed through the room during the Copenhagen Accord of 2009. Mohamed Nasheed, the president of the Maldives, posed this question in response to resistance to commit to a 1.5°C warming limit. Although the Maldives is a small nation whom one would not typically imagine being dominant on the UN stage, they, along with other small island nations, managed to steal the stage in Copenhagen and gather crucial support that led to the 1.5°C limit.

Low lying islands, especially those with limited financial resources, will be the first to suffer the severe consequences of climate change. Thus, it is in the interest of these nations to encourage larger, high emitting nations to limit their emissions and prevent further climate change. In 1990, a group of island nations from all different parts of the world formed the Alliance of Small Island States (AOSIS) in order to advocate for the common interests of small island states regarding climate change. The AOSIS initiated studies on the difference between 1.5 and 2 degrees of warming which led to the conclusion that the difference between this seemingly insignificant half a degree could be the difference between entire islands, such as Tuvalu, being inhabitable or not.

Once knowing how crucial it would be to limit warming to 1.5°C, different campaigns were launched to create support for making this an official limit. One of these campaigns, started in St. Lucia, coined the slogan “1.5°C to stay alive” which has become the catchphrase of this movement. AOSIS, along with individual island nations gradually gained the support of other nations which eventually led to the successful implementation of their requested 1.5°C limit as a part of the Paris Agreement. 

What happens if we go beyond 1.5°C?

After understanding what the 1.5 degree limit is and how it came to be, you may find yourself wondering what would actually happen if the world warmed more than 1.5 degrees. After all, 1.5 sounds like a reasonably small number, but in terms of climate change it has major implications. To put this number into context, it helps to know that the Earth is already 1.2°C warmer overall than it was in preindustrial times. But, just because the average warming across the globe is only 1.2°C, does not mean that that level of warming is ubiquitous across the globe. Some regions have already reached 1.5°C of warming and that means that if the global average went that high, some places would be even warmer. In fact, 20-40% of people already live in regions that have, for at least one season, exhibited warming of 1.5°C above pre industrial levels.

With the level of warming we have now, we already see widespread effects of climate change. Some islands have already disappeared, disastrous wildfires and are ever more prevalent, and extended droughts and heavy rainfall and flooding are both common occurrences. Thus, if we already see this at a global warming level of 1.2 degrees, it will only get worse at 1.5, and even more catastrophic at 2.

In 2018, the IPCC (Intergovernmental Panel on Climate Change) produced a special report that highlights some of the differences between 1.5 and 2°C warming. Some of the most severe examples of this include the projection that with 1.5°C warming, the arctic would be iceless every 100 years while with 2°C warming, this would happen every 10 years. Other effects include the bleaching of nearly all coral reefs after 2°C warming as well as more severe heat waves and higher sea levels. The report also describes economic and social challenges of these changes. For example, destruction of coral reefs could lead to declines in tourism in certain areas and therefore negatively impact regional economies. Thus, according to climate research, there is a vast difference between 1.5 and 2 degrees that we will be able to feel the effects of. 

This infographic about the sustainable development goal regarding climate action highlights how difficult it will be for us to achieve the 1.5 degree limit if we continue emitting at our current rates.

Are we on track to go beyond 1.5°C?

The answer is yes. We do not know for certain how warm the Earth will be in the future because we do not know how much we will reduce our emissions. While there are some efforts currently being made to reduce emissions, they are nowhere near close enough to reduce global warming to 1.5°C. Which means the Earth will warm much more than that. So, we now come back to the beginning of our story in which a number of small island nations banded together and convinced the world that limiting warming was something worth fighting for. While this was an important triumph, it seems like we are not willing enough to actually follow the guidelines of the Paris agreement which many tried so hard to push for. So in the end, the very countries that fought for this treaty will likely be uninhabitable in due time. 

Are you curious about the sources I used for this blogpost? Then click here to find links to all the sources I used.