Cold snaps during global warming are not actually a paradox, here’s why

Why do cold snaps persist if the Earth is warming? This question has popped up in various forms online, especially on social media. Climate contrarians often use it as a rhetorical question to make the false claim that ‘global warming must not be happening if we still experience cold weather’. 

Others may ask this question out of genuine curiosity – after all, it might be confusing to hear that the planet is warming if you are shivering in a cold spell.  

But does anything actually prevent global warming and cold snaps from coexisting? Not at all. Cold snaps (short periods of very cold weather) occur when there are large southward dips in the jet stream – strong winds 5 to 7 miles (8 to 11 kilometers) above Earth’s surface that blow west to east (Figure 1).

It’s clear that global warming has not stopped this process because climate scientists know for certain that Earth is warming and that cold snaps are still occurring. But that doesn’t answer the more interesting question of why.

The simple answer is that global warming does not stop Earth’s seasons from changing – thus allowing for winter weather – nor does it stop atmospheric circulation patterns that drive weather fluctuations. To dig deeper on this, we will explore what global warming is and – very importantly – what it isn’t, and how this ties into cold weather and cold snaps. 

Later, we will share comments Science Feedback received from five climate scientists on this topic and explore a hotly debated theory surrounding it. 

Global warming is making winters warmer, but that doesn’t mean cold weather will suddenly disappear

To understand why global warming doesn’t just stop cold weather from happening, it’s important to know both what global warming is and what it isn’t. 

The term ‘global warming’ does not imply that ‘everywhere is hot all the time’. Instead, it means that average global temperatures – measured from locations across Earth – have risen over the long term (typically decades or more). (See our past review on climate vs. weather). 

With the massive scale of our planet, this can be tricky to visualize. To simplify this, imagine heating up food. If you stick a large ham in the oven, for example, the ham is not instantly hot. Parts of the ham remain cold, while other spots heat up more quickly. 

By the same token, cold temperatures occurring somewhere on Earth does not mean the Earth is not warming overall. Moreover, Earth is far more complex than a piece of food in an oven – it is a massive rotating planet with large circulating systems like oceans and atmospheric layers that move and store heat around Earth. 

Given the complexity of our dynamic planet, scientists look at average global temperatures over decades or more. Looking at long-term averages in this way allows climate scientists to identify clear climate trends that might otherwise be obscured by short-term weather fluctuations (over days, weeks, or months). And what do they find?

Evidence from decades of research shows – without a shadow of doubt – that Earth has been warming since the industrial revolution in the late 1800s^[1]. This recent warming has been driven by human activities – such as burning fossil fuels – which have increased the greenhouse gases like carbon dioxide (CO₂) in our atmosphere^[1]. These greenhouse gases increase global temperatures by trapping outgoing energy/radiation (heat) that would otherwise escape to space. 

This process is known as the greenhouse effect – something we’ve covered in depth in past reviews – and it creates an energy imbalance in Earth’s climate, causing it to warm over time. So, if the planet is warming, why do we still experience cold weather? Put simply, global warming does not stop seasons – like winter – which are driven by Earth’s orbit and tilt relative to the sun.

• Learn why seasons occur

  Seasons occur because Earth’s axis of rotation is tilted relative to the sun (see figure below). This tilt causes Earth’s northern or southern hemisphere to be closer to the Sun at different periods of Earth’s orbit. Whichever hemisphere is tilted toward the sun will experience summer, while the other experiences winter. 

  

  Diagram showing why Earth’s tilt allows the northern and southern hemispheres of our planet to experience seasons differently as we orbit the sun. During the part of Earth’s orbit when the northern hemisphere is tilted toward the sun (as shown above), it will be summer in the northern hemisphere, and winter in the southern hemisphere. And vice versa when the northern hemisphere is tilted away. Adapted from source: The Conversation

Although winters still occur in a warming climate, that doesn’t mean they aren’t changing. As explained by the Intergovernmental Panel on Climate Change (IPCC), winters in general are getting warmer, and cold snaps have become less frequent or less intense over most land areas globally since 1950^[1]. 

Figure 2 below from IPCC’s Sixth Assessment Report shows that the annual coldest temperature in most land regions has increased (i.e., gotten warmer) between 1960 to 2018^[1]. 

Looking specifically at mid-latitude regions in the northern hemisphere – an area that some claim has seen an increase in cold extremes – a 2024 peer-reviewed paper in Science Advances found a marked decrease in intensity of cold temperatures from 1971 to 2022^[2]. This trend is shown in Figure 3 by a decrease in the number of very cold days in winter over time (graph B) and by a warming trend of the coldest days each winter (graph A). 

Despite winters getting warmer, short periods of extreme cold (cold snaps) can still hit some regions quite hard. But this is no surprise to climate scientists. As Dr. Andreas Schmittner, Professor of Earth, Ocean, and Atmospheric Sciences at Oregon State University, explained to Science Feedback:

So what are the actual reasons for these cold snaps, and does global warming play a role? 

In the next section, we will share comments we received from five climate scientists about the factors driving cold snaps and why there is still debate surrounding global warming impacts on the polar vortex and jet stream. 

Cold snaps are part of Earth’s natural climate variability and can still occur while Earth warms

Cold snaps – likely due to their extreme nature – seem to trigger questions about global warming. 

A question about cold snaps and global warming was even brought up in a recent NBC segment that went viral on Facebook. Al Roker, one of NBC’s weather presenters, claimed: ‘Global planet warming allows some parts of the U.S. to be colder than usual because as warm air moves into the arctic, it weakens the polar vortex and allows cold air to move south’. The video gathered over 420,000 views and sparked many debates in the comments section – most of which were started by climate change deniers. 

Although the persistence of cold snaps in a warming climate is not a surprise to climate scientists, Roker’s specific claim tying in Arctic warming actually touches on a hotly debated topic among climate scientists. 

To learn more about cold snaps, we reached out to several climate scientists. One of whom was Dr. Jennifer Francis, Senior Scientist at the Woodwell Climate Research Center, who researches how warming in the Arctic impacts weather patterns in mid-latitude regions. Francis explained:

These dips naturally occur when the jet streams weaken and become wavier, allowing cold air to flow down from the Arctic into mid-latitude regions like the U.S., bringing exceptionally cold temperatures with it. This concept is depicted in Figure 4 below. 

This is a well-known phenomenon among climate scientists and occurs as part of Earth’s natural climate variability. However, research papers over the last 12 years have argued that rising temperatures in the Arctic – which has been warming four times faster than the global average since 1979^[3] – are leading to a wavier jet stream and thus a higher likelihood of cold extremes in mid-latitude regions in the northern hemisphere. 

This is the root of Roker’s recent claims, but it is also a hotly debated topic among climate scientists. While Roker portrayed a mostly-accurate picture of why cold snaps generally occur, some key context was missing. When Science Feedback asked about Roker’s general claim, Francis explained:

Beyond a minor terminology mix-up, the main issue with Roker’s claim is that it connects these cold snaps to rapid Arctic warming – and, thus, global warming. In reality, these jet stream dips happen as part of Earth’s natural variability, with or without global warming. Climate scientists are studying ways in which current global warming may be affecting certain behaviors of the jet stream, but the verdict isn’t out yet.  

As explained by Dr. Adam Sobel, Professor of Applied Physics and Applied Mathematics and of Earth and Environmental Sciences at Columbia University:

This was the general sentiment from several of the climate scientists we spoke with. However, one of the scientists Science Feedback contacted, Dr. Francis, believes that although jet stream troughs occur naturally, global warming could be increasing their waviness through the rapid – and disproportionate – Arctic warming we noted earlier. Francis explains:

When Science Feedback asked if any evidence suggests that human-caused global warming is directly causing jet stream waviness to increase, or if it is more loosely connected, Francis explained:

Francis explained that rapid warming in the Arctic is reducing the north-south temperature difference (temperature gradient), which makes ‘blocks’ – high-pressure areas in the atmosphere that are nearly stationary – more likely to form. “These blocks are like eddies in a river that become separated from the main flow and can swirl in one place for a long time,” Francis explains. “A favored location of blocks is near Greenland, which is associated with upstream troughs in the jet stream that create cold spells.”

The second piece of evidence comes from the fact that the Barents/Kara Seas area (north of western Russia) is warming faster than most places on Earth – Francis explains*:

*Note: For more details about this evidence, see Francis’ full response in the Scientists’ Feedback section at the end of this article.

Other climate scientists argue that the theory has not yet been validated. Regarding the possibility that a weaker and wavier jet stream could lead to more hot and cold extremes, Dr. Michael Wehner, Senior Scientists at the Lawrence Berkeley National Laboratory, explained:

Conclusion

Global warming has not stopped all cold weather and cold snaps from happening, but this isn’t a surprise to climate scientists. Since 1950, on a global scale – and over most land areas – winters have been getting warmer as global temperatures have risen, and cold snaps have become less frequent or intense. Despite global warming, seasons will continue as part of Earth’s natural cycle (a result of Earth’s tilt and orbit), and along with it, hotter and colder periods (summer and winter).

Cold snaps are also part of Earth’s natural climate variability, but they have decreased at a global scale in frequency or severity as the planet has warmed. Cold snaps in the northern hemisphere can occur with or without global warming, as disruptions to the polar vortex (cold air currents circling high above the Arctic) cause the jet stream (fast west-to-east flowing winds at lower altitudes) to dip southward, carrying cold air to mid-latitude regions (like the U.S.). Some have argued that global warming has affected the jet stream in a way that is making cold extremes in these regions more likely, but the theory is still hotly debated among climate scientists. 

Questions to scientists from Science Feedback:

1. Does the claim made by Al Roker accurately describe why some parts of the U.S. can experience cold periods while the planet is overall warming? Or is the ‘weakening/more wavy polar vortex from arctic warming’ he describes just one mechanism among others that might cause this to occur?
2. Is there sufficient evidence that anthropogenic climate change – especially in the arctic region – has affected the polar vortex in a way that causes (not just correlates with) cold weather anomalies in lower latitudes (e.g., the U.S.)? Or could this mechanism – if there is good evidence for it – fall within natural variability?
3. Are climate scientists confident about how anthropogenic climate change has impacted (or will impact) winter temperatures?

References

• 1 – IPCC (2021). Sixth Assessment Report.
• 2 – Blackport et al. (2024) Models and observations agree on fewer and milder midlatitude cold extremes even over recent decades of rapid Arctic warming. Science Advances. 
• 3 – Rantanen et al. (2022) The Arctic has warmed nearly four times faster than the globe since 1979. Nature Communications Earth & Environment
• 4 – Cohen et al. (2021) Linking Arctic variability and change with extreme winter weather in the United States. Science. 
• 5 – Hanna et al. (2024) Influence of high-latitude blocking and the northern stratospheric polar vortex on cold-air outbreaks under Arctic amplification of global warming. Environmental Research Climate.