Global Warming...New Report...and it ain't happy news

High levels of carbon dioxide in the atmosphere are a major driver of climate change. At the same time, increased CO2 can encourage plants to grow faster, allowing them to absorb more carbon and potentially slow warming. That benefit, however, depends on whether plants have access to enough nitrogen, a nutrient that is essential for growth. Scientists have only recently taken a closer look at how much nitrogen is actually available in nature. New research involving the University of Graz shows that the so-called CO2 fertilization effect has been significantly overstated.

Plants cannot use nitrogen on their own. The nutrient must first be converted into a usable form through a process called nitrogen fixation, which relies on microorganisms in the soil. This process takes place in natural ecosystems as well as on farmland. "While this process has been significantly overestimated in nature, it has increased by 75 percent over the past 20 years due to agriculture," says Bettina Weber, a biologist at the University of Graz, summarizing findings from a study published earlier this year.

Building on those results, a new analysis shows that the way nitrogen fixation is calculated in some Earth System models has now been reassessed. These models are widely used to project climate trends and inform major assessments, including the World Climate Report. The updated findings were published in the scientific journal PNAS.

New Findings Prompt Climate Model Revisions

The study was led by Sian Kou-Giesbrecht of Simon Fraser University in Burnaby, Canada. The work was carried out by an international research group focused on biological nitrogen fixation, which includes Bettina Weber. This working group receives support from the U.S. Geological Survey (USGS) John Wesley Powell Centre for Analysis and Synthesis.

"We compared different Earth System models with current nitrogen fixation values and found that they overestimate the nitrogen fixation rate on natural surfaces by about 50 percent," Weber explains. Because plants depend on this process to access nitrogen, the overestimate has meaningful consequences. According to the study, it results in an overall reduction of about 11 percent in the projected CO2 fertilization effect.

Why Updating Models Is Critical

Weber emphasizes the importance of adjusting climate models to reflect these updated measurements. "This is because gases such as nitrogen oxides and nitrous oxide are produced as part of the nitrogen cycle. These can be released into the atmosphere through conversion processes and alter or disrupt climate processes." Accurately accounting for nitrogen dynamics, she says, is essential for making reliable predictions about how ecosystems and the climate will respond in the future.

Summary
Copernicus data show that 2025 was the third warmest year on record1, only marginally (0.01°C) cooler than 2023, and 0.13°C cooler than 2024 – the warmest year on record. The past 11 years have been the 11 warmest on record. Global temperatures from the past three years (2023-2025) averaged more than 1.5°C above the pre-industrial level (1850–1900). This marks the first time a three-year period has exceeded the 1.5°C limit. Air temperature over global land areas was second warmest, whilst the Antarctic saw its warmest annual temperature on record and the Arctic its 2nd warmest.

The Environmental Protection Agency repealed the bedrock scientific finding that greenhouse gases threaten human life and well being. It means the agency can no longer regulate them.

The world is closer than thought to a “point of no return” after which runaway global heating cannot be stopped, scientists have said.

Continued global heating could trigger climate tipping points, leading to a cascade of further tipping points and feedback loops, they said. This would lock the world into a new and hellish “hothouse Earth” climate far worse than the 2-3C temperature rise the world is on track to reach. The climate would also be very different to the benign conditions of the past 11,000 years, during which the whole of human civilisation developed.

At just 1.3C of global heating in recent years, extreme weather is already taking lives and destroying livelihoods across the globe. At 3-4C, “the economy and society will cease to function as we know it”, scientists said last week, but a hothouse Earth would be even more fiery.

The public and politicians were largely unaware of the risk of passing the point of no return, the researchers said. The group said they were issuing their warning because while rapid and immediate cuts to fossil fuel burning were challenging, reversing course was likely to be impossible once on the path to a hothouse Earth, even if emissions were eventually slashed.

It was difficult to predict when climate tipping points would be triggered, making precaution vital, said Dr Christopher Wolf, a scientist at Terrestrial Ecosystems Research Associates in the US. Wolf is a member of a study team that includes Prof Johan Rockström at the Potsdam Institute for Climate Impact Research in Germany and Prof Hans Joachim Schellnhuber at the International Institute for Applied Systems Analysis in Austria.

“Crossing even some of the thresholds could commit the planet to a hothouse trajectory,” said Wolf. “Policymakers and the public remain largely unaware of the risks posed by what would effectively be a point-of-no-return transition.

“It’s likely that global temperatures are [already] as warm as, or warmer than, at any point in the last 125,000 years and that climate change is advancing faster than many scientists predicted.”

It is also likely that carbon dioxide levels are the highest they have been in at least 2m years.

Prof Tim Lenton, an expert on tipping points at the University of Exeter in the UK, said: “We know we are running profound risks on the current climate trajectory, which we can’t rule out could turn into a trajectory towards a much less habitable state of the climate for us. However, we don’t need to be heading towards a hothouse Earth for there to be profound risks to humanity and our societies – these will already be upon us if we continue to 3C global warming.”

The assessment, which was published in the journal One Earth, synthesised recent scientific findings on climate feedback loops and 16 tipping elements. The tipping elements include the Greenland and Antarctic ice sheets, mountain glaciers, polar sea ice, sub-Arctic forests and permafrost, the Amazon rainforest and the Atlantic meridional overturning circulation (Amoc), a system of ocean currents that strongly influences the global climate.

Tipping may already be happening in Greenland and west Antarctica, with permafrost, mountain glaciers and the Amazon rainforest appearing to be on the verge, the scientists said.

“Research shows that several Earth system components may be closer to destabilising than once believed,” they concluded. “While the exact risk is uncertain, it is clear that current climate [action] commitments are insufficient.”

Prof William Ripple, at Oregon State University, US, who led the analysis, said: “The Amoc is already showing signs of weakening, and this could increase the risk of Amazon dieback. Carbon released by an Amazon dieback would further amplify global warming and interact with other feedback loops. We need to act quickly on our rapidly dwindling opportunities to prevent dangerous and unmanageable climate outcomes.”

Scientists warned in 2018 of the prospect of a hothouse Earth. In this scenario, global temperature stays significantly above the 4C rise of current worst-case climate scenarios for thousands of years, driving a huge rise in sea level that drowns coastal cities. The scientists said then that the “impacts of a hothouse Earth pathway on human societies would likely be massive, sometimes abrupt, and undoubtedly disruptive”.

It was a major success for the Obama administration to make progress on climate protection through the Clean Air Act. Other climate protection initiatives have repeatedly failed in Congress, and to this day there is no separate climate protection law in the United States. However, Congress no longer had to approve climate regulations under the Clean Air Act separately. Trump now wants to abolish this option. He announced this shortly after taking office a year ago, and the move had been long anticipated.

Quote:

The Environmental Protection Agency repealed the bedrock scientific finding that greenhouse gases threaten human life and well being. It means the agency can no longer regulate them.

Trump Administration Erases the Government’s Power to Fight Climate Change [NYT, no paywall]

But I guess the threat posed by gay-friendly kids' books in public libraries really should take priority.

[...]
Fewer greenhouse gas emissions restrictions
[...]
Cheaper cars in the US (but they'll be harder to export)
[...]
Nuisance lawsuits
[...]
Public health
[...]
Falling behind in the global renewables race
[...]
Less industry regulation
[...]

Abstract

The onset of animal breeding activity is often accompanied by auditory signals, typically produced by males, that indicate reproductive status to potential mates and competitors. Here, using male anuran advertisement calls as a case study, we present the novel hypothesis that characteristics of ectotherm auditory signals that are modulated by temperature may also serve as bioclimatic indicators of the suitability of proximal abiotic conditions for reproduction. According to this hypothesis, thermal constraints on signal characteristics, such as call rate and duration, may facilitate tracking of environmental conditions by females. Through integrative analysis of empirical ecological studies, we demonstrate how variation in call properties may influence female reproductive physiology and behavior. We then outline how this proposed mechanism may enable environmental tracking and phenological shifts with climate change, provide guidelines for experimentally testing this hypothesis, and discuss applications of findings from this research to conservation management for species of concern.