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Could the Earth surpass its 1.5C limit earlier than initially projected?


When James Hansen speaks, he tends to attract attention, which is understandable. Hansen, who is often referred to as the pioneer of climate science, gained worldwide recognition in June 1988 while serving as the director of the Nasa Goddard Institute for Space Studies.

He was asked to address a US Senate committee, where he cautioned that Nasa had a 99% certainty that human activity was causing global warming through greenhouse gas emissions, and that the probability of severe weather events was on the rise. This influential testimony, given 35 years ago, is widely acknowledged by scientists and historians as a crucial moment in raising public awareness of the impending climate crisis.

For over 40 years, Hansen was employed by Nasa and eventually shifted his focus to promoting and advocating for action as his repeated cautions were not adequately listened to. Currently at 82 years old, he serves as an adjunct professor at Columbia University and regularly shares analyses of the most recent evidence on climate change.

The latest commentary, co-authored by three colleagues under the title “El Niño fizzles. Planet Earth Sizzles. Why?”, investigates why this year is predicted to be the warmest on record. Their most noteworthy finding, particularly in relation to the global reaction to the climate emergency, suggests that by the beginning of next year, the planet may have experienced a 1.5C increase in temperature from the historical average.

The goal of limiting heating to 1.5C is a crucial international ambition outlined in the significant Paris climate agreement. It has been widely embraced as a safeguard to prevent worsening destruction that impacts people, their livelihoods, and the environment.

According to the Guardian, scientists are shocked by the average global temperature last month, which was 1.7C or 1.8C higher than historic levels and over 0.5C warmer than the previous record for September.

This doesn’t mean the 1.5C guardrail is gone – that will only happen if temperatures stay that high for an extended period. That has generally been considered to be years away. The Intergovernmental Panel on Climate Change said only that it was likely within the next two decades. Hansen argues recent temperatures challenge that.

In the previous four months, the Earth’s temperature has been 0.44 degrees Celsius higher than it was in 2015. This year was chosen because it was the last time we experienced an El Niño, which typically causes the planet to warm. The scientists suggest that if this trend continues until the northern spring (southern autumn), the average temperature over a 12-month period will be at least 1.6 degrees Celsius higher than temperatures from over a hundred years ago.

According to them, if 1.5C is reached, it would be considered practically achieved and there would be no need to contemplate for 20 years about whether we have truly reached this goal, as suggested by the IPCC. However, they believe that the Earth’s significant energy imbalance guarantees that the global temperature will continue to rise in the foreseeable future.

Due to the ongoing focus on achieving the 1.5C target, there is a possibility that some individuals may perceive any potential failure as a defeat in the fight against the climate crisis. This may lead them to consider giving up. However, this is not the viewpoint shared by the scientific community, and not all climate experts concur that there is sufficient evidence to prove a rapid increase in global warming.

Hansen and his colleagues primarily focus on the factors contributing to the recent increase in heat. They propose that the current El Niño event is not as significant as past occurrences, and may end up being less intense than the “super” El Niños of 1997-98 and 2015-16.

One possible reason for a sudden increase in temperature could be a decrease in man-made aerosols, specifically from power plants and factories in China and the global shipping industry. Aerosols can have a cooling effect by interacting with sunlight and clouds, which has previously counteracted some of the heat caused by greenhouse gases in the atmosphere. However, reducing aerosol pollution for the purpose of improving air quality may reveal the true extent of human-caused warming in the world.

Hansen has referred to this as the Faustian trade-off of climate change. The use of fossil fuels results in the release of both aerosols and greenhouse gases, but while the cooling impact of aerosols lasts for only a few days, the warming effects of greenhouse gases can persist for centuries. He predicts that the consequences of this trade-off, such as a rapid rise in global temperatures, will eventually have to be faced.

The other area of significant change this year is Antarctica, where warming this year has been off-the-charts. Until recently, there has not been a global heating signal over much of Antarctica despite scientists having long expected that polar regions would warm faster than the rest of the planet. Hansen and co join other scientists who have noted that events this year, particularly a sharp fall in sea ice cover, may indicate this has changed and the continent is becoming an important contributor to global heating.

It is worth noting that not all experts in climate science share the same level of concern as Hansen and his colleagues regarding the possibility of surpassing the 1.5C threshold. The discussion about whether the protective measure has already been exceeded is not a recent one. In 2021, the Australian Academy of Science stirred up considerable controversy when it claimed that it would be nearly impossible to remain below this limit.

Michael Mann, an esteemed author and professor at the University of Pennsylvania, is one of the experts who advises against drawing too much meaning from a brief time period this year. This could possibly be attributed to the effects of El Niño and natural fluctuations in addition to the consistent, long-term impact of human-caused climate change.

According to Mark Howden, a faculty member at the Australian National University and vice-chair of the Intergovernmental Panel on Climate Change, the current heat is alarming because it aligns with predictions made by scientists for a long time.

According to him, the role of aerosols in driving high temperatures is still a topic of discussion. He points out that there was not a similar increase in temperatures when the use of aerosols significantly decreased due to Covid-19 shutdowns in 2020. He also mentions that it may take some time before we can determine if the temperature has reached 1.5C, as this assessment requires long-term data.

However, Howden acknowledges that we are quickly moving towards this direction and governments are not taking the necessary actions in response to compelling evidence that both human and environmental safety are in jeopardy.

What is the significance of surpassing 1.5C? It has significant implications for millions of individuals and numerous species. However, it is important to note that this threshold was somewhat arbitrarily chosen and influenced by political factors. It could have been set at 1.2C, 1.4C, or 1.6C.

The basic idea conveyed by numerous scientists is as straightforward as a guardrail. It’s the same one Howden shared on social media half a decade ago: every small increment of temperature counts, every year counts, every decision counts.

As always, the question remains: who is paying attention?

Source: theguardian.com