The Wonderful Issues of Climate Change - Post #1 - Climate and Weather

Original Date: January 10, 2024; Revised February 25, 2024

Author: Tim Platnich

Climate change is in the news daily. Over a series of posts on this blog, I intend to discuss various concepts of climate change. The intent is to elucidate the language, concepts, science and issues involved with climate change.

Let's start with the definitions of 'climate' and 'climate change'. As we shall see in the following paragraphs, we must also distinguish between climate and weather.

Climate and weather are different concepts. We are repeatedly advised not to confuse the two. Weather has only limited predictability. Beyond a week or two individual weather systems are unpredictable [IPCC 2001]. Indeed, weather is a chaotic system highly dependent on initial conditions ["Chaos" - James Gleick]. Weather is measured in terms of days, months, seasons and even years, whereas climate is measured in terms of decades or longer. Changes in the weather from one year to another does not constitute a change in climate. Changes in the weather over decades is climate change.

“Weather describes the conditions of the atmosphere at a certain place and time with reference to temperature, pressure, humidity, wind, and other key parameters (meteorological elements); the presence of clouds, precipitation; and the occurrence of special phenomena, such as thunderstorms, dust storms, tornadoes, and others ”.[IPCC 2013 AR5]

When we refer to weather, we are typically referring to temperature, precipitation, cloudiness and wind. When we look at a weather forecast, we are interested in a limited period of time and what the high and low temperatures are going to be in the time-period; whether it is going to rain or snow and how much; and whether wind, extreme or otherwise, is going to be a factor.

When we refer to climate, we are talking in generalities. Climate is the average of weather over decades [“Unsettled: What Climate Science Tells Us, What It Doesn’t, and Why It Matters” by Steven Koonin]. What is the climate of Alberta or of Calgary specifically? What high and low temperatures can we expect in July? What amount of snow can we expect in February? Is Calgary prone to hail storms, tornadoes, flooding or drought?

'Climate' refers to the average weather in terms of the mean and its variability over a certain time-span and a certain area [IPCC 2001]. The relevant quantities of climate are most often surface variables such as temperature, precipitation and wind, classically averaged over a period of 30 years [IPCC AR5].

Climates change. Different weather patterns over short periods of time do not constitute climate change. Calgary may experience a hotter than usual July in one or two years (as in 2022 and 2023). This does not indicate climate change. If Calgary experiences hotter than usual months of July year after year for decades, climate change is indicated. Our expectations of Calgary temperatures in July would reflect the new reality.

A Calgary heat wave is no more evidence of global warming than a cold snap is evidence of global cooling. These are weather events, nothing more. For example, February 2019, was the coldest February in Calgary since 1936 [Calgary Herald, Feb 25, 2019]. This is not evidence of global cooling any more than the hottest July is evidence of global warming. Another example: in 2021 the South Pole experienced the coldest winter ever recorded [Washington Post, October 2, 2021, citing data from the Amundsen-Scott South Pole Station]. This is not evidence of global cooling. None of these events are evidence of climate change. These are weather events.

“[S]tatistically significant variations of the mean state of the climate or of its variability, typically persisting for decades or longer, are referred to as “climate change”. [IPCC AR5]

“Because the climate is an average over many years, it changes slowly. It takes at least a decade of observations to define a climate, and two or more decades to identify a change in it.”[Unsettled, at p. 28]

From the forgoing, one can see that caution is needed when reading media reports that claim a specific weather event is evidence of climate change. A weather event is a data point. This data point, taken together with comparable data points over decades may be evidence of climate change.