The internationally agreed threshold to prevent the Earth from spiraling into a new superheated era will be “passed for all practical purposes” during 2024, the man known as the godfather of climate science has warned.
James Hansen, the former NASA scientist credited for alerting the world to the dangers of climate change in the 1980s, said that global heating caused by the burning of fossil fuels, amplified by the naturally reoccurring El Niño climatic event, will by May push temperatures to as much as 1.7C (3F) above the average experienced before industrialization.
This temperature high, measured over the 12-month period to May, will not by itself break the commitment made by the world’s governments to limit global heating to 1.5C (2.7F) above the time before the dominance of coal, oil and gas. Scientists say the 1.5C ceiling cannot be considered breached until a string of several years exceed this limit, with this moment considered most likely to happen at some point in the 2030s.
But Hansen said that even after the waning of El Niño, which typically drives up average global heat, the span of subsequent years will, taken together, still average at the 1.5C limit. The heating of the world from greenhouse gas emissions is being reinforced by knock-on impacts, Hansen said, such as the melting of the planet’s ice, which is making the surface darker and therefore absorbing even more sunlight.
“We are now in the process of moving into the 1.5C world,” Hansen told the Guardian. “You can bet $100 to a donut on this and be sure of getting a free donut, if you can find a sucker willing to take the bet.”
In a bulletin issued with two other climate researchers, Hansen states that “the 1.5C global warming ceiling has been passed for all practical purposes because the large planetary energy imbalance assures that global temperature is heading still higher”. Hansen has promoted a view, disputed by some other climate scientists, that the rate of global heating is accelerating due to a widening gap between the amount of energy being absorbed by the Earth from the sun and the amount returning to space.
Hansen, renowned for his role in publicly revealing the onset of the greenhouse effect to the US Congress in 1988, added that the looming loss of the 1.5C guardrail should provide a jolt the United Nations’ Intergovernmental Panel on Climate Change (IPCC), the foremost body of climate science that has charted pathways to avoid breaching the target.
“Passing through the 1.5C world is a significant milestone because it shows that the story being told by the United Nations, with the acquiescence of its scientific advisory body, the IPCC, is a load of bullshit,” Hansen said.
“We are not moving into a 1.5C world, we are briefly passing through it in 2024. We will pass through the 2C (3.6F) world in the 2030s unless we take purposeful actions to affect the planet’s energy balance.”
Hansen’s assertion that this year will herald the start of an escalating 1.5C era has received a cautious response from other scientists contacted by the Guardian. Drew Shindell, a climate scientist at Duke University, said this year was an “unusually warm one” due to El Niño and that following years will best judge whether the 1.5C target has vanished.
But he added the world was closing in on this point and the 1.5C limit would probably be hit “in the 2020s and not the 2030s any more given recent years have warmed so rapidly, so Jim’s larger point that we’re moving rapidly into the post-1.5C era is correct in my opinion.
“To my mind, whether it’s 2024 or 2027 makes little difference in the end to informing our actions – we have to change course immediately or we’ll lose our ability to keep below 2C the same way the 1.5C goal has now become out of reach,” Shindell said.
Zeke Hausfather, a climate scientist at Stripe and Berkeley Earth, said “I disagree a bit with Hansen” that global temperatures will not be less than 1.4C above pre-industrial times once there is a countervailing La Niña, a reverse climatic condition to El Niño. “But longer term those sorts of temperatures will no longer be seen as the Earth continues to warm,” Hausfather said, adding that he still expected the long-term average to fully pass 1.5C in the early 2030s.
Andrew Dessler, climate researcher at Texas A&M University, said that he also expected it to take “10-ish years” to break the 1.5C barrier, but that Hansen’s views should be taken seriously. “Jim is probably the greatest climate scientist in history, so I am hesitant to disagree with him because perhaps he’ll turn out to be right,” Dessler said.
Even if the world’s temperature is to break the 1.5C barrier, researchers stress that this doesn’t mean that all will irretrievably be lost, with every fraction of a degree added, or not, significant in shaping the severity of climate impacts. By current government pledges to cut emissions – if not their actual actions to date – the world is still heading for at least 2.5C (4.5F) warming by the end of this century.
“I do think that in worrying about some particular threshold we are addressing the wrong question,” said Kerry Emanuel, a climate and meteorological expert at the Massachusetts Institute of Technology. “There are no magic numbers in climate change, just rapidly growing risks.”
Emanuel pointed to recent severe heatwaves, fires and storms that are already being supercharged by global heating of around 1.2C (2.1F) above what it was a little more than a century ago. “Perhaps, once half the population of the planet has experienced at least one of these weather catastrophes, they will get their leaders to act,” Emanuel said. “I hope it doesn’t take that much pain.”
What If the Best-Case Scenario for Climate Change Were Better?
In a report in Bloomberg on Jan 9, 2024, Sana Pashankar said:
In 2019, an ecologist at Oregon State University named William Ripple led the writing of an article declaring “clearly and unequivocally that planet Earth is facing a climate emergency,” and laying out “vital signs” of a planet in distress. More than 11,000 scientists around the world co-signed the article before its publication.
Now, Ripple and colleagues argue the scenarios that climate experts use to grapple with the future aren’t adequate. In a paper published Tuesday in Environmental Research Letters, they call for climate models to incorporate a new “restorative pathway,” one on which the world would not just slash greenhouse gas emissions but bring about greater ecological health and social justice in the process.
The report said:
Climate scientists currently rely on five different scenarios of the future, a group known as the shared socioeconomic pathways (SSPs). Developed by an international team and used by the United Nations’ Intergovernmental Panel on Climate Change, these pathways track how global heating could play out in the years to come, based on how quickly countries cut emissions and on socioeconomic factors like population, education and technological development.
In the current best-case scenario — SSP1 — the world reaches net zero around 2050. In the worst-case (SSP5), the world accelerates the exploitation of fossil fuels, doubling emissions by 2050 and raising temperatures 4.4C by the end of the century.
The restorative pathway grafts ecological and equity goals onto the downward emissions curve of SSP1. On the pathway, global croplands would decline by 2100, compared to expanding under SSP1, while per-capita gross domestic product would taper off, instead of rising as it does on the SSP1 trajectory. The new pathway could include “greater convergence of per-capita GDP, meat consumption, and energy use throughout the world” to promote equality between the Global North and Global South, the authors write.
We asked Ripple to say more about the proposal. This interview has been edited and condensed for length and clarity.
What Is The Restorative Pathway?
The Bloomberg report said:
What we are proposing is an environmentally and socially just scenario. And we are doing this to address converging crises including climate change, biodiversity loss and social injustice.
We are proposing something holistic — to have solutions to multiple challenges at the same time rather than work on them piecemeal. So we think that climate change is not a standalone problem, but it is a symptom of a much larger problem. And the larger one involves economics, it involves social inequality and it involves nature conservation, in addition to greenhouse gas emissions that are so commonly talked about.
We have not done all the calculations on the exact reduction in emissions, but in general our scenario is similar to SSP1, with a dramatic decrease in greenhouse gas emissions as we move forward.
How Was It Developed?
We compiled a diverse set of Earth system variables for the last 500 years, including fossil fuel emissions, human population, GDP, land use, greenhouse gas emissions and temperature. Moving forward to 2100, we used SSP projections for some of the variables, but we differ in how we deal with future croplands and [the greenhouse gas] nitrous oxide.
How Else Is This Scenario Different From The Existing SSPs?
The report said:
Compared to the SSPs, our scenario is less reliant on technological developments to remove carbon dioxide from the atmosphere. In addition, it places greater emphasis on addressing inequality in the over-exploitation of the planet, and we are projecting improved biodiversity in our scenario. And another major difference is what we project forward for GDP. Our scenario stabilizes GDP over time rather than having it continuously go upward.
What type of global developments or policies would be needed to achieve this scenario?
Economically, there might be a global policy of a carbon tax, and that would do two things. It could reduce fossil fuel emissions and it could help redistribute wealth where the wealthy would be paying more carbon taxes.
We also are pushing for the conservation of nature, where we would be achieving more forest lands, and we’d be taking fewer lands out of nature and into cropland. What we are proposing for more equity globally is higher levels of education for girls and women, resulting in low fertility rates with higher standards of living.
According to the paper, on this scenario, global GDP would stabilize and the top 10% of income would get more evenly divided among the population. What would this look like for the global economy?
Since business-as-usual isn’t working and infinite economic growth is problematic, we need to shift towards a post-growth economy where the quality of life and societal wellbeing are prioritized. We would need specialists in ecological economics to help plan an era of different economics.
