The term “global warming” is typically used to describe increasing global temperatures as a result of human emissions of carbon dioxide (CO2) and other greenhouse gases.
However, unusually cold events are often portrayed as being made worse by human activity, as a result of increased variability or a disruption of the “polar vortex” in a fast-warming world.
There is significant debate in the scientific community about whether rapid Arctic warming and sea ice loss could disrupt atmospheric circulation patterns and lead to cold-air outbreaks in the northern hemisphere mid-latitude regions.
In a new analysis, Carbon Brief shows that few places in the world have seen an increase in extreme cold days over the past 55 years.
If climate change is influencing atmospheric circulation, any effects on extreme cold appear to be more than compensated by the rapid winter warming the world has experienced.
A controversial hypothesis
In an episode of Marketplace’s How We Survive podcast last year, the host – US radio journalist Kai Ryssdal – noted that climate change is expected to cause “hotter hots [and] colder colds in unexpected parts of the world”.
This is not an uncommon sentiment, with the media commonly attributing extreme cold events to human activity, particularly during episodes of bitter cold or polar-vortex events.
Some researchers have argued that these extreme cold snaps might be becoming more frequent due to reduced sea ice and Arctic amplification – the phenomenon where the Arctic warms more quickly than the global average.
At the core of the hypothesis that Arctic warming could influence mid-latitude cold extremes is the fact that a rapidly warming Arctic changes the temperature difference between the poles and the equator.
Normally, the strong contrast in temperature between these regions drives key patterns of atmospheric circulation, including the jet stream. According to proponents of this theory, when Arctic temperatures rise faster than those farther south, atmospheric circulation can weaken, meander, or buckle more frequently. As a result, cold polar air can spill down into areas that are usually less frigid.
A related argument focuses on how diminished sea ice – particularly in the Barents and Kara seas – might disrupt the atmosphere. Less sea ice means more heat and moisture escapes from the ocean surface into the air, which can potentially alter weather patterns downstream. This can boost the odds of “blocking high” weather systems, or unusual circulation patterns that pull cold air into mid-latitudes.
However, there are relatively few studies that attribute an increase in cold extremes – or an individual extreme cold event – to human activity.
Carbon Brief’s attribution map – which charts extreme weather events around the world and their links to human-caused warming – includes 33 studies that examine extreme cold events specifically.
Of these, 24 studies found that the extreme cold was made less likely due to climate change, six found no discernible human influence and three found insufficient data to conclude either way. Only one extreme event attribution study in the database found that a cold extreme – severe frosts in Western Australia in 2016 – was made more likely due to climate change. However, even that study noted that “warmer temperatures may have offset or countered this effect of the circulation driver”.
Many climate scientists disagree with the hypothesis that warming could lead to increased cold outbreaks, arguing that cold extremes are decreasing overall in a warming world.
Others contend that causality cannot yet be proved and that both models and observations provide limited support for a significant role of climate change in mid-latitude cold events.
In addition, observed data reveals that, although cold spells still occur, they have become less frequent and less intense over recent decades. Most modeling studies do not consistently reproduce more frequent or severe cold outbreaks. Instead, they often show that the overall warming trend dominates, making cold extremes rarer over time.
This suggests that, if there were a connection between climate change and extreme cold events, the long-term warming trend will still likely lead to fewer, milder cold outbreaks – and that any effect from Arctic amplification would be relatively small.
Have any regions experienced increased cold events?
To help assess the effects of climate change on extreme cold events, Carbon Brief used gridded daily minimum global temperature data from Berkeley Earth to calculate how the temperatures of the coldest 5% of the days of the year have changed since the 1970s.
Minimum daily temperatures reflect the single coldest measurement taken over the course of the day. (While the coldest 5% of days is a somewhat arbitrary number, the results are largely similar for the coldest 10%, 5%, 2%, 1%, or the single coldest day of the year.)
The figure below shows the results for every one-by-one degree latitude-longitude grid cell on the Earth’s land (a size approximately equivalent to 100km by 100km). Grid cells coloured red experienced a decrease in extreme cold days, while those coloured blue had more extreme cold days.
The vast majority of the planet has seen a strong decrease in extreme cold events, with the largest declines seen in high-latitude northern hemisphere regions (which have also experienced the fastest rate of warming overall).
The few regions that have seen an increase in extreme cold events tend to be those with the slowest average rates of warming, including India, South Africa and Antarctica.
In India, this has likely been influenced by rapid increases in air pollution – particularly cooling sulfate aerosols – over this period. Causes of more extreme cold events in Antarctica are less clear, though it is possible that they could be linked to the seasonal loss of ozone layer over the past 50 years.
Another way to assess changes in cold events is to look at the change in the number of days where any hour of the day – that is, the daily minimum temperature – is below freezing (0C, 32F). The map below shows the change in average annual freezing days between 1970 and 2024.
The map shows dramatic shifts in the number of freezing days in much of the high-latitude northern hemisphere, with nearly a month fewer freezing days over the Himalayas, eastern Europe and parts of Canada and the western US over the past 50 years.
(White areas on the graph – such as much of the tropics and subtropics – represent regions of the world where temperatures below freezing almost never occur and thus changes over time cannot be calculated.)
Fewer cold outbreaks in the US
A sizable portion of the academic research on cold outbreaks has been focused on the contiguous US, as it is a region prone to occasional extreme cold conditions caused by intrusions of Arctic air.
The map below shows there has been a warming trend in the coldest days of the year across virtually the entire US over the past 50 years.
This suggests that the effect of Arctic amplification on cold-air patterns is smaller than the strong winter warming trend.
Almost no regions of the US have seen a cooling trend in the 5% coldest days of the year – and higher latitude regions have tended to experience the fastest winter warming.
There has been a slight cooling trend in the coldest days of the year in northern Mexico and slower warming in California, Arizona, southern New Mexico and southern Texas.
Similarly, the figure below examines the change in days where minimum temperatures are below freezing in the US.
It shows that there are, on average, 13 fewer days below freezing each year compared to the 1970s. Or, to put it another way, there is half a month where daily minimum temperatures are no longer cold enough for icy and snowy conditions to occur.
Increasingly rare cold spells
The latest climate models overwhelmingly project that cold extremes will continue to diminish as greenhouse gas concentrations rise.
This means that, even if certain patterns occasionally transport freezing polar air southward, winters on the whole are likely to be milder than in the past.
However, the scientific understanding of precisely how Arctic warming might – or might not – influence mid-latitude weather is still evolving.
Researchers continue to refine models, incorporate better reanalysis data and examine how changes in atmospheric circulation dynamics might play out under different scenarios. Additional data – especially over multiple decades – will help clarify whether the Arctic’s role in mid-latitude cold extremes is significant or overstated.
For now, observations over the past 50 years generally show a world with fewer cold extremes – and projections point toward increasingly rare cold spells in the future.
The post Factcheck: Climate change is not making extreme cold more common appeared first on Carbon Brief.
Factcheck: Climate change is not making extreme cold more common
Three countries have been named by the Paris Agreement’s compliance committee for failing to submit a nationally determined contribution (NDC) and repeatedly snubbing offers of help with their climate plans.
After months of internal debate over whether to identify serial non-responders, the Paris Agreement’s Implementation and Compliance Committee (PAICC) named the three countries which have failed to engage with it over their NDCs on Friday.
It named Democratic Republic of Congo, Senegal and North Korea in a footnote of its annual report, adding that it decided to name them “with a view to facilitating engagement”, adding that representatives of the three nations had been invited to its meeting in early 2027 “with the purpose of identifying any challenges and constraints”.
“The Committee noted the importance of Parties engaging with the Committee in a timely manner, while noting that some delays may be due to the national capabilities and circumstances of the Parties”, the report said.
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Paris Agreement committee snubbed over missing NDC climate plans
Many governments have still not submitted a nationally determined contribution to the UN, breaching a key requirement of the Paris Agreement
In July, PAICC said 12 countries had ignored its repeated attempts to discuss why they had not published an NDC as required every five years under the 2015 Paris accord.
Members of the committee had been divided over whether to name them, but at a September meeting decided to do so in their annual report to the annual climate COP summit.
By the time the report was published on Friday, only Congo, Senegal and North Korea “had not communicated an NDC or submitted a [Biennial Transparency Report] and had not yet responded to any of the Committee’s notifications, despite several reminders issued by the Committee in this regard”.
Rainforest and renewable energy ambitions
The silence from Congo and Senegal is notable because the former is home to much of the Congo Basin rainforest while the latter has sought billions of dollars in climate finance to support its renewable energy ambitions.
After Brazil, Congo has more rainforest than any country in the world. This forest, and the country’s peatlands, absorb huge amounts of greenhouse gas but are fast being lost to expanding farmland, charcoal production, logging and mining.
Senegal signed a Just Energy Transition Partnership with Canada and wealthy European nations in 2023, to help it meet its renewable energy targets under the-then government of Macky Sall. It was chair of the Least Developed Countries group between January 2022 and December 2023.
Tejas Rao, who is researching the PAICC as part of a doctoral thesis at Cambridge University, said the governments of the three countries should engage with the committee.
“Engagement costs these governments very little and the committee has shown it will listen,” he said.
“Silence leaves the committee with no basis to help, and it leaves the [governments] exposed to the narrative that they are simply disengaged,” he told Climate Home News.
Paris Agreement requirement
The 2015 Paris Agreement requires all parties to publish an NDC every five years outlining their emissions reduction targets, with each plan meant to be more ambitious than the country’s last NDC.
The latest set – the third round of plans, with new targets for 2035 – was due in February 2025. While most countries missed this deadline, all but around 30 – mostly small emitters but including Egypt, Vietnam and Argentina – have now submitted them.
Over the year, the PAICC – which is made up of government climate officials from developed and developing countries – has been communicating with governments that have not submitted NDCs and trying to overcome barriers to them doing so.
Some nations have cited exceptional circumstances as the reason for not submitting an NDC, a process that requires a significant amount of work in tracking emissions and consulting on how to curb them across the economy. For example, a letter from a Sudanese official to the PAICC, seen by Climate Home News, said that the country’s civil war had led to the suspension of its NDC preparation.
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The US and Iran are not signed up to the Paris Agreement and so do not have active NDCs, nor does Taiwan, which is not a UN member state.
Rao said that because the PAICC is “facilitative and non-punitive”, naming the countries “is meant to open a door, not close one – the invited consultation is the point”.
“In recent months, governments that explained their constraints, whether capacity, finance or domestic process, have been met with follow-up and support rather than sanction, and the number of silent governments has fallen sharply,” Rao said.
The post Paris Agreement committee names three countries snubbing it over NDCs appeared first on Climate Home News.
Paris Agreement committee names three countries snubbing it over NDCs