Climate vs. weather: a deep dive on the key differences

What’s the difference between ‘climate’ and ‘weather’? Although they are related, these are actually two distinct concepts and they are measured at very different timescales. Despite this, some people use these terms interchangeably, leading to confusion and misinformation about climate change.

For example, a Facebook post from 9 August 2024 received over 15,000 interactions after stating “I remember when climate change was just called Spring, Summer, Autumn, & Winter!”

And this type of claim is far from novel. Over the years, similar misleading talking points have circulated online, incorrectly conflating climate change with short-term weather or seasonal changes – below are some examples:

• “Back in my day we used to call climate change the weather”
• “It’s cold outside … what happened to global warming?”
• “Hot and cold weather periods happened in the past, so recent climate change is normal”
• “Today’s climate changes are just part of the natural cycle of seasons”
• “If we can’t even predict the weather 100% over days to weeks, how could we possibly predict future climate change?”

Most of these claims could easily be settled by looking up the definitions of climate and weather, which are markedly different: weather is measured at daily and weekly timescales, and climate over decades or more. However, going a step deeper raises an interesting question: why does climate change differ from short-term weather changes? We will investigate this below.

Climate and weather are different concepts – climate change occurs at much longer timescales

Weather is a key part of our daily lives and one of the most common topics that springs up in our daily conversations. Daily and weekly weather changes are unavoidable and often dictate how we plan our activities and travel. What about climate change?

Conversations about climate change have ramped up in recent years as scientists have unequivocally found^[1] that changes are already underway, with more severe climate changes anticipated in our future^[2]. But where do scientists draw the line between weather and climate?

Climate and weather are markedly different, and the key difference lies in the timescales at which they occur. The World Meteorological Organization (WMO) explains:

“Weather is the state of the atmosphere at a particular time, as defined by the various meteorological elements, including temperature, precipitation, atmospheric pressure, wind and humidity.” 

They also note that weather describes short-term changes (i.e., hourly and daily) in “sunshine, rain, snow, hail, sleet, mist, blizzards, storms, and similar phenomena.”

Although weather plays an important role in the definition of ‘climate’, they have distinct meanings. In contrast to the short time frame of weather changes, Earth’s climate is assessed over much longer periods of time. As explained by WMO, “Climate is the average weather conditions for a particular location over a long period of time, ranging from months to thousands or millions of years. WMO uses a 30-year period to determine the average climate.” By definitions alone, there is a clear difference in timescales between ‘weather’ and ‘climate’. But how else do they differ?

Earth’s climate is complex, and when referred to more broadly, it involves more than just long-term average weather changes. The Intergovernmental Panel on Climate Change (IPCC) explains that climate describes the average weather conditions over long periods of time; however, they also explain that “climate in a wider sense is the state, including a statistical description, of the climate system”^[3].

This broader definition makes two important distinctions: first, it defines climate not only as weather patterns, but more holistically as a climate system. And secondly, it mentions ‘statistical descriptions’ – something which allows scientists to convey the patterns they observe in data with added context. For example, using averages of temperature data from around the globe, scientists can better capture and explain the overall changes on Earth, rather than relying on data from one location or region. Before we dive into more examples, what exactly is the ‘climate system’?

The climate system includes the following components of Earth and the interactions between them^[3] (Figure 1):

• Atmosphere (Earth’s gaseous outer layers)
• Hydrosphere (Earth’s water)
• Cryosphere (Earth’s ice and snow)
• Lithosphere (Earth’s crust and upper mantle)
• Biosphere (Earth’s ecosystem of all living things)

The Earth is in a constant state of change – a dynamic interplay between these different components that leads to different states in the climate system. For example, as carbon dioxide (CO₂) increases in Earth’s atmosphere, temperatures rise through the greenhouse gas effect^[1,5,6]. However, there is not only input of CO₂ into the atmosphere through processes on land, but also an exchange of gases (e.g., H₂O, CO₂, etc.) between the oceans and the atmosphere. Thus, components of Earth’s climate do not change in isolation, but rather as part of a dynamic and interconnected system.

Given the dynamic nature of the climate system, scientists need ways to identify when the changes are significant. This is where the ‘statistical descriptions’ we referenced earlier play an important role. Statistics can be thought of as a common language that scientists use to determine and convey what data shows (e.g., how is the average global surface temperature changing over time?).

The IPCC explains that “Climate change refers to a change in the state of the climate that can be identified (e.g., by using statistical tests) by changes in the mean [average] and/or the variability of its properties and that persists for an extended period, typically decades or longer.”^[3]

In other words, even though Earth’s climate does vary over time (referred to as ‘natural internal variability’), scientists are able to use statistics to identify when this variability or the climate’s ‘average’ conditions have changed.

For example, using statistical descriptions, scientists can analyze and describe global temperature trends in several decades of data and identify trends despite short-term fluctuations in this data. Statistics are a tool that allows climate scientists to look at data and say ‘yes, temperatures have risen and fallen over shorter periods – with some days or weeks being exceptionally hotter or colder than normal – but here’s how those ups and downs are changing over long periods of time’. If the data shows that nearly all temperature measurements are rising – that is, the highs are getting higher, but so too are the lows – climate scientists can conclude that temperatures are increasing overall. Without statistical descriptions, it would be very difficult to pick out this long-term climate ‘signal’ out of the short-term ‘noise’.

To visualize how these patterns can emerge from fluctuating data, we can use the analogy of a person walking their meandering dog, and imagine the paths they trace out along the way.

Imagine watching from a bird’s-eye view as a person walks their dog on a leash between imaginary points ‘A’ and ‘B’ (Figure 2). In this scenario, the person walks a straight line from point A to point B, but their dog wanders along the way. If you traced out the person’s path, a clear pattern would emerge – a straight route from point A to point B (i.e., a trend).

But if you look at the dog’s winding path their overall direction or pattern would be harder to discern. However, if you look at the trend of the dog’s general path – simplified as a ‘best-fit’ straight line – it would look similar to that of their owner.

The dog’s slight deviations are like the fluctuations that occur with weather in the short term, and the person’s path is an analogy for an overall climate trend – i.e., how the ‘ups and downs’ change over the long term. This visualization demonstrates how broader climate trends (e.g., global warming) and patterns can still be identified over longer time periods, despite short-term weather fluctuations (e.g., an unusually cold week).

However, the analogy above obviously oversimplifies what climate scientists have to do to analyze and discern climate patterns. So with the complexity of Earth’s climate, how do scientists determine changes within it? They monitor ‘climate indicators’ – changes in parts of the climate system (e.g., ocean heat content, global mean surface air temperatures, global mean sea level, etc.) that indicate changes in the state of Earth’s climate. By analyzing and monitoring different indicators in the climate system, scientists are able to assess what changes have occurred and how humans have contributed to those changes.

Figure 3 presents a number of these indicators, their changes over periods ranging from decades to over 100 years, and an assessment of human contribution to those changes. These findings come from IPCC’s Climate Change 2023 Synthesis Report, which the IPCC explains is “the most comprehensive assessment of climate change undertaken thus far by the IPCC”^[2].

Notice that Figure 3 shows the degree of certainty or confidence associated with both the observed changes and human contribution to those changes. Here, again, is an example of the importance of the ‘statistical descriptions’ mentioned earlier. Some data have a higher ‘statistical significance’, which gives scientists better certainty about the patterns and relationships they observe in the data.

There are inherent uncertainties in models and methods of analyzing trends in climate data; however, for certain trends and observations, the evidence is so robust, and the data so clear, that scientists can draw conclusions that approach ‘virtual certainty’ or can even be considered a fact.

For example, Figure 3 clearly indicates that certain observed changes – such as rising global mean surface air temperatures since 1850-1900^[2] – have occurred and that humans have contributed to this change. Both are supported so robustly by scientific evidence that the IPCC labels them as facts – the highest level of certainty they assign.

Tying in the ‘dog walking’ analogy from earlier, Figure 4 shows that global surface temperature has fluctuated since 1850 (analogous to the path of the meandering dog on leash), but still shows a clear trend of a sharp rise over recent decades (analogous the path of the person walking the dog).

The findings presented in Figures 3 and 4 above settle a number of claims we mentioned in the introduction. For example, claims suggesting that current climate change is ‘the same as the hot and cold weather they had as kids’ are wrong in any interpretation. If these claims are, in fact, referring to weather, the statement is misleading because they incorrectly conflate climate and weather. If those statements are referring to the global climate, they are inaccurate, as shown by global surface temperature records (Figure 4).

As we explained earlier, climate and weather are not the same. People may have experienced short and/or local heat waves and bouts of cold weather. However, anecdotal evidence from one’s childhood does not overwrite the global warming trends scientists from around the world have unequivocally found in direct temperature observations^[2].

Additionally, the data from the entire observation period – i.e., the period for which we have direct temperature measurements – in Figure 4 dates back to 1850. That is far earlier than anyone currently alive was born, and therefore captures any period people (alive) experienced. And for that period, the IPCC explains that “Each of the last four decades has been successively warmer than any decade that preceded it since 1850.”^[7]

And claims that these changes are just ‘natural’ or due to the ‘natural cycle’ are also unfounded in the context of at least the last 2000 years. As explained in Figure 4 by the IPCC, “Human influence has warmed the climate at a rate that is unprecedented in at least the last 2000 years”.

Furthermore, as shown in Figure 4 above, scientists have modeled the global surface temperature changes over the period for which we have direct measurements under two scenarios: ‘natural and human drivers’ and ‘natural only’. The figure shows that the addition of human drivers – such as CO₂ emissions – lead to a greater rise in global temperatures that more closely match direct measurements, and that natural forces (i.e., solar and volcanic) alone fail to explain the recent rise in global temperatures.

Scientists have a high degree of certainty in several observed climate changes and their main drivers, so why do some people still question these changes?

Climate changes which occur over decades are much harder to ‘sense’ than the daily changes we experience with weather

Because climate trends occur over long periods, there can be a disconnect between what people ‘feel’ is happening with Earth’s climate – which they base on short-term weather – and what climate scientists have discovered by analyzing long-term data. However, this is no surprise, because people are used to monitoring weather changes over days or weeks – not decades, or more.

In other words, understanding the concept of weather change is a bit intuitive given our daily – or even hourly – experience of these changes. When we see gray billowy clouds roll in, we might expect rain. As the leaves begin to rustle, we can surmise that the wind is picking up. However, given the long time scales at which climate change is evaluated, the evidence is less tangible.

Perhaps this is one reason why climate change and weather change are easily conflated: climate change is harder to ‘validate’ in our day to day experiences, so it’s easier to just lump them together conceptually. However, although they are categorically different, climate can still influence weather events, as we will discuss below.

Short-term weather events are not climate trends; however, climate change can influence weather events on longer timescales

In the last section we explained that a key difference between climate and weather is their timescales. Climate change is monitored at longer timescales (e.g., typically decades or more), and weather is monitored at shorter timescales (e.g., days to weeks). So, by their very definitions, climate and weather are different concepts. However, they are still related; climate changes can influence weather patterns.

One short weather anomaly – such as an unusually cold week in summer – is not enough to draw conclusions about overall climate change trends. However, climate change can – and already has – altered the frequency and severity of certain weather events^[1]. The IPCC explains that “Regional changes in the intensity and frequency of climate extremes generally scale with global warming” and “that even relatively small incremental increases in global warming (+0.5°C) cause statistically significant changes in extremes on the global scale and for large regions (high confidence).”^[8]

There are several types of weather events which climate scientists are virtually certain have been influenced by climate change – and in some cases, that human activities have driven those changes. For example, the IPCC explains that the frequency and intensity of precipitation and extreme heat waves has increased over most land regions since the 1950s^[7]. At a global scale, the IPCC explains that it is virtually certain that this trend has been observed/detected and that human contribution is extremely likely to be the main contributor (Figure 5).

There are several other weather extremes that have changed on a global scale, as shown in Figure 5 below. (Note that there are other changes that the IPCC lists with ‘medium confidence’, but those below are listed as ‘likely’ or ‘virtually certain’).

Ideally, climate scientists would already be able to understand the effects of climate change on all types of weather equally. But this is not the case. For several reasons, understanding how climate change affects the frequency and severity of weather events is considerably more challenging for some weather types than it is for others^[1].

As the IPCC explains, “The level of complexity of the involved processes differs from one type of extreme to another, affecting our capability to detect, attribute and project changes in weather and climate extremes.”^[8] High-quality data for tornadoes, for example, is somewhat limited, making it challenging for scientists to determine changes in long-term trends. But uncertainty about changes in certain weather events is a far stretch from misleading claims that “scientists can’t predict the influence of climate on weather changes because short-term weather predictions are uncertain’. That claim is misleading because it suggests that the same uncertainties apply across all scales.

It may seem intuitive that short-term changes should be easier to predict than long-term changes; however, this assumes that weather and climate are measured using the same parameters. In other words, when forecasting climate changes, scientists aren’t predicting the inches of rainfall in some specific town, as meteorologists would for daily weather forecasts.

Instead, scientists generally monitor climate trends at broader scales. For example, in Figure 5, the IPCC lists some of the observed and detected climate trends at continental to global scales. One observed trend they note is a likely “increase in the frequency, intensity, and/or amount of heavy precipitation”^[1] at both global and continental scales.

When assessing these changes more broadly – as shown in the quote above – climate scientists have much higher certainty than they do trying to predict and detail the exact changes that will likely occur in a specific area (e.g., rainfall in a certain city). Their understanding of how and why certain changes unfold is borne out of a strong understanding of physical processes on Earth.

This can be explained with another simplified analogy of turning on a fireplace to warm a room. We have a physical understanding that fire creates heat, the heat will get trapped in the room, and the room’s temperature will start to rise. There’s a simple ‘cause and effect’ relationship there that we understand from a broad perspective. However, determining ‘how fast’, and ‘by how much’ the temperature will rise introduces more uncertainty and variables we would have to factor in. For example, is a window open? How big is the fire? And so on.

Similarly, there are physical processes on Earth that climate scientists strongly understand the consequences of. However, there are also uncertainties in assessing climate change, albeit far more complex ones. To assess climate change, scientists use paleoclimate records (i.e., reconstructions of past climates using lake and ocean sediments, glacial ice, etc.), recent climate measurements (e.g., temperature data), advanced climate models, and other methods – all with their own levels of uncertainty.

Due to these uncertainties, it is true that climate models cannot predict all future climate conditions with 100% accuracy – especially for every region. However, contrary to claims (reviewed here) that ‘less-than-perfect’ predictions indicate that “climate scientists lack the ability to predict climate change”, climate scientists have observed – and can anticipate – numerous climate changes with very high certainty.

The foundation of this certainty is built on climate scientists’ strong understanding of physical processes on Earth, as mentioned earlier. One example of this is their understanding of how rising CO₂ levels affect global temperatures. There is a clear, physical connection between CO₂ and global temperature rise, which allows scientists to quantify how much of the observed warming – which is occurring, as unequivocally shown by scientific evidence^[1] – is mainly driven by CO₂ added to the atmosphere through human activities. This well-known phenomenon of atmospheric CO₂ trapping heat on Earth – known as the greenhouse gas effect – among many other physical phenomena gives climate scientists a strong understanding of how changing conditions on Earth (e.g., CO₂ levels) will influence certain aspects of our future climate (e.g., global temperatures).

Conclusion

Climate and weather, although related, are distinctly different concepts. A key difference is their timescales by which they’re defined: weather is monitored over days to weeks, and climate typically over decades or more. Additionally, weather is the specific atmospheric conditions at a certain place and time, whereas climate looks at the average weather conditions over a longer period of time. A more holistic definition of climate includes statistical descriptions of the climate system, its various components – the atmosphere, cryosphere, hydrosphere, and so forth – and how they interact with each other. Short-term fluctuations (over days to weeks) and anomalies in weather (e.g., a few unusually hot or cold days) do not negate the well-observed climate change trends scientists have observed in recent times. For example, scientific evidence unequivocally shows that global warming is occurring.

Online claims that use anecdotal evidence to claim that these climate changes are ‘normal’ either in the context of ‘when they grew up’ or as part of the ‘natural cycle’ are inaccurate. Scientists have found that the past four decades have been progressively warmer than any preceding decades since 1850 in the observational record. Furthermore, paleoclimate data suggest that the current rate of global warming is unprecedented in the context of at least the last 2000 years. Therefore, it is clear that the current rates and conditions of climate change are unprecedented compared to what anyone alive experienced in the past. But more importantly, it is flawed reasoning to compare certain days or weeks of weather to long-term climate change trends; not only do they involve very different timescales, but there is also robust scientific evidence unequivocally showing that climate change is occurring.

REFERENCES

• 1 – IPCC (2021). Sixth Assessment Report.
• 2 – IPCC (2023) Climate Change 2023: Synthesis Report.
• 3 – IPCC (2018) Annex I: Glossary. In: Global Warming of 1.5°C.
• 4 – IPCC (2001) TAR Climate Change 2001: The Scientific Basis.
• 5 – Zhong and Haigh (2013) The greenhouse effect and carbon dioxide. Royal Meteorological Society Weather.
• 6 – Pierrehumbert (2011) Infrared radiation and planetary temperature. Physics Today.
• 7 – IPCC (2021) Summary for Policy Makers. In Climate Change 2021: The Physical Science Basis. Contribution of Working Group I to the Sixth Assessment Report of the Intergovernmental Panel on Climate Change
• 8 – IPCC (2021) Weather and Climate Extreme Events in a Changing Climate. In Climate Change 2021: The Physical Science Basis. Contribution of Working Group I to the Sixth Assessment Report of the Intergovernmental Panel on Climate Change