The Paris climate accord represented a historic step towards a safer future for humanity on Earth when it was adopted in 2015. The accord strived to keep global warming below 2 pre-industrial levels with the aim of limiting the increase to 1.5 if possible. It has been signed by 196 parties around the world, representing the vast majority of humanity.
But over the next eight years, the Arctic region experienced record-breaking temperatures, heatwaves hit many parts of Asia, and Australia was faced with unprecedented flooding and wildfires. These events remind us of the dangers associated with climate collapse. Our newly published research argues instead that humanity is safe only at 1 global warming or below.
While an extreme event cannot be attributed solely to global warming, scientific studies have shown that such events are much more likely in a warmer world. Since the Paris Agreement, our understanding of the impacts of global warming has also improved.
Sea level rise is an inevitable consequence of global warming. This is due to a combination of increased land ice melt and warmer oceans, causing the volume of ocean water to increase. Recent research shows that to eliminate the human-induced component of sea level rise, we need to go back to temperatures last seen in the pre-industrial era (usually around 1850).
Perhaps more concerning are tipping points in the climate system that are effectively irreversible on human timescales if passed. Two of these tipping points involve the melting of the Greenland and West Antarctica ice sheets. Together, these sheets contain enough ice to raise global sea levels by more than ten metres.
Read more: Greenland is melting: we need to worry about what’s happening on the world’s largest island
The temperature threshold for these ice sheets is uncertain, but we know it is close to 1.5 global warming above pre-industrial levels. There is also evidence to suggest that the threshold may have already been crossed in part of West Antarctica.
A temperature change of 1.5 might seem quite small. But it’s worth noting that the rise of modern civilization and the agricultural revolution some 12,000 years ago took place during a period of exceptionally stable temperatures.
Our food production, global infrastructure, and ecosystem services (the goods and services ecosystems provide to humans) are all intimately tied to that stable climate. For example, historical evidence shows that a period called the Little Ice Age (1400-1850), when glaciers grew extensively in the Northern Hemisphere and frost fairs were held annually on the River Thames, was caused by a change in temperature much smaller than only about 0.3.
A recent review of ongoing research in this area introduces a concept called Earth system boundaries, which define various thresholds beyond which life on our planet would suffer substantial damage. To avoid exceeding multiple critical limits, the authors emphasize the need to limit the temperature rise to 1 or less.
In our new research, we also argue that warming more than 1 risks dangerous and harmful outcomes. This potentially includes sea level rise of several meters, more intense hurricanes, and more frequent extreme weather.
Cheaper renewable energy
Although we are already 1.2 above pre-industrial temperatures, reducing global temperatures is not an impossible task. Our research presents a roadmap based on current technologies that can help us work towards the first warming goal. We don’t need to pull a technology rabbit out of the hat, but instead need to invest in and implement existing approaches, such as renewable energy, at scale.
Renewable energy sources have become increasingly affordable over time. Between 2010 and 2021, the cost of generating electricity from solar energy decreased by 88%, while wind energy saw a reduction of 67% in the same period. The cost of energy storage in batteries (for when the availability of wind and sunlight is low) has also decreased, by 70% between 2014 and 2020.
The cost disparity between renewable energy and alternative sources such as nuclear and fossil fuels is now enormous, three to four times the difference.
In addition to being affordable, renewable energy sources are available in abundance and could quickly meet society’s energy needs. Massive capacity expansions are also currently underway around the world, which will further strengthen the renewable energy sector. Global solar power generation capacity, for example, is expected to double in 2023 and 2024.
Removal of carbon dioxide from the atmosphere
Affordable renewable energy will enable our energy systems to move away from fossil fuels. But it also provides the means to directly remove CO2 from the atmosphere on a large scale.
Removing CO is critical to keeping warming at 1 or less, even though it requires a significant amount of energy. According to the research, achieving a safe climate would require dedicating between 5% and 10% of total power generation demand to effective CO2 removal. This represents a realistic and feasible policy option.
Various measures are used to remove CO from the atmosphere. These include nature-based solutions such as reforestation as well as direct carbon capture and storage in the air. Trees absorb CO2 from the atmosphere through photosynthesis and then lock it up for centuries.
Direct air capture technology was originally developed in the 1960s for purifying the air on submarines and spacecraft. But it has since been further adapted for use on land. When combined with underground storage methods, such as the CO stone conversion process, this technology provides a safe and permanent method of removing CO from the atmosphere.
Our paper demonstrates that the tools and technology exist to achieve a safer, healthier and more prosperous future, and that it is economically feasible to do so. What seems to be missing is the will of society and, consequently, the political conviction and commitment to achieve it.
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