In February 2025, Professor James Hansen and his co-authors published a shocking new study (‘Global Warming Has Accelerated: Are the United Nations and the Public Well-Informed?‘) in the journal Environment: Science and Policy for Sustainable Development.
The study carries weight given that Hansen first brought the climate crisis to the world’s attention in 1988 and is regarded by many as the leading climate scientist in the world. It stretches over 38 pages and contains no shortage of warnings about the dire predicament we’re in.
In this post, I unpack some of the points that stood out for me.
Key messages
- “Shutdown of the Atlantic Meridional Overturning Circulation (AMOC) is likely within the next 20-30 years, unless actions are taken to reduce global warming.”
- The planet’s albedo (the reflectivity of lighter coloured landscapes such as ice sheets and glaciers), has “decreased about 0.5%… since 2010.” This change in albedo, “is equivalent to an increase of CO2 by 138 ppm, from the 419 ppm actually measured at the beginning of 2024 to 557 ppm.”
- “Several meters” of sea level rise is predicted over the next “50-150 years”.
- The Paris target of limiting temperature rises to 1.5C by the year 2100, has already been “breached, for all practical purposes.”
- On our current trajectory, we’re heading for 2C – 3C of warming, which would “push the climate system beyond the Point of No Return.”
- We desperately need an “effective, knowledgeable political party that takes no money from special interests.”
Global shipping aerosols
Over the last two years, temperatures have jumped by over 0.4C. This temperature rise was affected by the El Niño event which typically causes temperatures to rise. However, the warming experienced was “twice as large as expected” for this El Niño event, which confounded many climate scientists.
Hansen’s team attribute most of the extra warming to a change in shipping emissions. In 2020, the International Maritime Organization (IMO) banned aerosols which affect human health, including a reduction in sulphur content from 3.5% to 0.5%. This led to the use of fuel oils which produced less of these aerosols. How could this effect temperatures in a negative way?
“Aerosols are small particles that serve as cloud formation nuclei. Their most important effect is to increase the extent and brightness of clouds, which reflect sunlight and have a cooling effect on Earth. When aerosols – and thus clouds – are reduced, Earth is darker and absorbs more sunlight, thus enhancing global warming.”
Given that the change in the production of these aerosols are likely to be permanent, the study argues that warming will continue due to reduced albedo. This despite the fact that the El Niño has finished and we’re heading towards a cooler La Niña phase. The study states that, “We expect that global temperature will not fall much below +1.5°C level, instead oscillating near or above that level for the next few years.”
Climate targets and temperature rises
Given that the world has hit the 1.5C threshold, and that the study believes this level of warming will continue as a result of reduced aerosol emissions, Hansen’s team argues that, “the widely discussed 1.5 °C temperature threshold,” has been, “breached, for all practical purposes.”
The reason why this matters is because the 1.5C threshold is what politicians have signed themselves up to, over and over again. They’ve said at countless summits since Paris in 2015 (when the goal first came about) that they aim to keep the global temperature rise below 1.5C by the end of the century. However, not only have we temporarily breached this goal, but Hansen believes we will continue to hover around it for the next few years at least. They make a valid argument that the goal is dead for “practical purposes.”
And yet as recently as COP29, which took place in November 2024, politicians from around the world agreed at the summit to pursue, “efforts to limit the temperature increase to 1.5 °C above pre-industrial levels, recognizing that this would significantly reduce the risks and impacts of climate change.”
As such, there is a yawning gulf between what climate scientists are saying, and the self-constructed bubble that politicians live in. A bubble possibly lined with incentives from the fossil fuel industry.
For those of us living in reality, the 1.5C target is dead. According to the Copernicus Climate Change Service, 2024 was the first year to breach the 1.5C threshold. In addition, January 2025 was the 18th month out of the last 19 months, in which global temperatures were above 1.5C. Hansen’s team argues this trend will continue for years to come.
Hansen’s team believe that the world is on track for 2C – 3C of warming. This ties in with forecasts from Climate Action Tracker; they analysed recent global climate policies and estimated that the world is on track for 2.7C of warming by 2100. Hansen’s study says that warming in this range would “push the climate system beyond the Point of No Return, locking in sea level rise of many meters and worldwide climate change, including more powerful storms and more extreme floods, heat waves, and droughts.”
That’s the headline. That’s what our politicians would tell us if they were being honest. But being honest would also mean that they’d have to admit to failing us on purpose. Since 1988, politicians have had 37 years to tackle this crisis, but instead they’ve chosen to kick the can down the road. However, it appears that we’re running out of road…
Climate impacts
The most disturbing forecast from this study was the prediction that the Atlantic Meridional Overturning Circulation (AMOC), which acts like a massive conveyor belt transferring heat from the tropics to the poles, and cooler water back from the poles to the tropics, may shutdown within 20-30 years. The authors believe this may happen because melting ice in the polar regions has led to an enormous injection of freshwater into the North Atlantic, which will likely increase as global warming accelerates. This freshwater injection means that seawater in these areas is more diluted and less salty. This matters because AMOC relies on dense seawater (seawater is heavier than freshwater) sinking close to the poles, pulling in surface water from the tropics. However, as the polar ice caps melt and more freshwater enters the ocean at the poles, it becomes less dense and doesn’t sink as easily. Thus, the conveyor belt at first begins to slow down (there are already signs of this), before eventually switching off.
It’s hard to capture in scientific terms just what kind of upheaval this would lead too, but the study mentions it would lock in several meters of sea level rise, and they refer to the shutdown of AMOC as a “point of no return.” More on this in the next section.
Another terrifying titbit from the paper states that the albedo of earth has decreased by 0.5% since 2010. This may not sound like much, but it’s actually massive. What it means is that there are less light coloured surfaces on earth (e.g. white ice sheets) to reflect heat back out to space. So instead, we have more dark coloured surfaces (e.g. open ocean), which absorbs more heat and leads to more warming. Just how big is this 0.5% reduction in albedo?
Hansen’s team use carbon dioxide (CO2) concentrations in the atmosphere as a means of comparison. To give some context, prior to the industrial revolution in 1750, CO2 concentrations in the atmosphere were 280ppm. The ‘safe’ level of CO2 is estimated to be around 350ppm. Anything over 400ppm takes us into very dangerous territory. In early 2024, the concentration of CO2 in the atmosphere was 419ppm. Hansen’s team note that the 0.5% reduction in albedo since 2010 is equivalent to raising CO2 concentrations by another 138ppm. So that would take 2024’s CO2 concentrations from 419ppm to 557ppm. To repeat, this change in albedo has happened within just 15 years…
Facts like this often make me think, that if there was a siren to sound the alarm on climate breakdown, it would be wailing at an ear-splitting volume 24 hours a day, 7 days a week. Perhaps that might wake-up politicians from their fossil fuel induced coma.
Elsewhere in the paper, I found it quite interesting to read the explanation around thermal inertia – something I’ve long known about, but never seen quantified. Thermal inertia relates to the fact that the ocean absorbs a lot of the heating we’ve caused, but it takes time for oceans to heat up themselves. Thus, heating up oceans effectively stores up problems for the future. The study quantifies this as follows: “About 40% of the eventual (equilibrium) warming is achieved in 10 years, 60% in 100 years, and 90 percent in 1,000 years.”
As the study notes, this is both a stroke of fortune, and a cause for great concern. We’ve been lucky that a lot of excess warming has been stored away by the oceans. But we’re also very unlucky, because with time, that warming will hit with full force. Thus, even if we stopped all emissions today – heating would continue for many centuries to come as the oceans continue to warm up.
Other climate impacts listed in the study refer to what’s happening today with more severe and more frequent tropical storms, thunderstorms, tornadoes and floods. These “are driven by high sea surface temperature and a warmer atmosphere that holds more water vapor. Higher global temperature also increases the intensity of heat waves and – at the times and places of dry weather – high temperature increases drought intensity, including “flash droughts” that develop rapidly, even in regions with adequate average rainfall.”
The Eemian interglacial period, and the “Point of No Return”
The study says that the Earth is now as warm as the Eemian interglacial period, which dates back 120,000 years.
During the late Eemian, the AMOC shutdown which had a massive affect on the climate. AMOC transports the equivalent of 1,000 trillion watts of heat from the South to the North. As a result of the shutdown, much of the heat remained in the Southern Ocean, where it may have played a role in collapsing the West Antarctic ice sheet. This would explain why this period saw several meters of sea level rise within a single century. The West Antarctic ice sheet is particularly vulnerable as it juts into the sea and rests on bedrock that lies hundreds of meters below the water line. Therefore as oceans warm, this ice sheet starts melting at the base and is susceptible to rapid disintegration.
The study spoke about AMOC shutdown being a “Point of No Return.” Tied very close to this (as explained above) is the related “Point of No Return” of the collapse of the West Antarctic ice sheet. This would lead to several meters of sea level rise. What would happen if the West Antarctic ice sheet collapses?
More than half the world’s largest cities would be submerged, as would large parts of the US, China, Bangladesh, the Netherlands, and island nations. Largescale emigration would ensue as people flee coastal areas and disaster zones. Sea levels won’t stabilise after the collapse of the West Antarctic ice sheet. This is because Greenland and Antarctica have a lot of ice in contact with warming seas – enough to raise sea levels by 15-25m. During the early Pliocene – a comparable time in Earth’s history when temperatures were 2C warmer than pre-industrial times (bear in mind we’re heading for around 2.7C of warming this century) – sea level was 15-25m higher. Hansen’s team say that, “Sea level change takes time, so coastlines would be continually retreating.” A major uncertainty is the point at which ice shelf melting must reach, before the collapse of the ice sheet becomes unavoidable.
The study notes that, “Global emissions will remain high and climate will pass the Point of No Return, if the atmosphere continues to be a free dumping ground for fossil fuel emissions.” Even though China and India are responsible for much of today’s emissions, the study notes that historical emissions are driving climate breakdown, with the US and Europe holding responsibility for the highest cumulative emissions.
Geoengineering
“Today’s older generations – despite having adequate information – failed to stem climate change or set the planet on a course to avoid growing climate disasters.”
Hansen’s team says they don’t recommend climate interventions such as geoengineering. I feel very strongly that we should avoid geoengineering as we’ve already tampered with the climate system too much (and just about everything else besides) and created problem upon problem.
Yet, the study says that even though they don’t recommend geoengineering, it might be worth exploring it – in order to give younger generations another option in their toolbox, should they need it to prevent climate chaos. Hansen’s team says, “We do not subscribe to the opinion that such knowledge will necessarily decrease public desire to slow and reverse growth of atmospheric greenhouse gases; on the contrary, knowledge of such research may increase public pressure to reduce greenhouse gas amounts.”
Conclusion
“Failure to be realistic in climate assessment and failure to call out the fecklessness of current policies to stem global warming is not helpful to young people.”
This study makes for dire reading. It’s horrific to think that politicians have purposefully put us in this position, having failed to address this crisis for 37 years, including 29 annual COP climate summits, where even as late as 2024, they still continue chasing targets that are no longer achievable.
Hansen says, “what is needed is a strengthened resolve to transition away from fossil fuels and adequate funding to assist nations presently suffering climate disasters.” He says that young generations are increasingly angry with governments, and anxious about their future, “They see shootings in their schools. They see growing wars in the world. They see climate changing. In all cases, they see innocent people suffering with ineffectual government response. Yet they have faith in science.”
Hansen says he is optimistic because, “Young people have demonstrated an extraordinary ability to affect politics without taking any money from special interests.” This is something he believes is urgently needed – an effective political party that doesn’t take money from special interests. Hansen’s team says, “We should be eager at the opportunity to save not only our democratic system, but our climate and all that entails for humanity and nature.” This is a conclusion I’ve also reached.
In the 20th century, we saw the pesticide industry lobby their way out of regulations. We saw the industries producing toxic PFAs get away with poisoning people and the natural world. We saw the tobacco industry lobby hard against the science linking smoking to cancer for decades. We saw the CFC industry push back for many years so they could continue selling their ozone-depleting chemicals, which enlarged the hole in the ozone layer before the Montreal Protocol was enacted. We saw the fossil fuel industry sow denial and doubt to delay any meaningful regulation on their climate killing products – something that still goes on today. And now in the 21st century, we’re witnessing the tech industry (who spent $957m on lobbying in 2023), lobby hard to prevent regulations on AI systems which threaten algorithmic extinction. As long as politicians can be bought by an industry – regardless of what nefarious industry it happens to be – our civilisation will be at risk.
To tackle our biggest problems, involves taking on some of the wealthiest and most powerful industries in the world. We can’t do that if our politicians are being lobbied and incentivised to protect them, against the interests of society. Thus, urgent democratic reform must happen if we are to survive this turbulent and defining century, which will reshape civilisation one way or another. This is why I’m pushing for participatory and deliberative democracy, including citizens’ assemblies as one solution.
Politicians have shown themselves to be incapable of tackling our greatest challenges. So it’s left to us to do all the heavy lifting – and there is a great deal to be done, which only increases with each passing day.
A time of change is upon us. We must work together to determine whether that change will see society thrive, or come to a chaotic end.
My cli-fi children’s picture book, Nanook and the Melting Arctic is available from Amazon’s global stores including Amazon UK and Amazon US. My eco-fiction children’s picture book, Hedgey-A and the Honey Bees about how pesticides affect bees, is available on Amazon’s global stores including Amazon UK and Amazon US.