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What is climate change?

June 17, 2021 | Charles Lin


Image by cocoparisienne from Pixabay

Climate is average weather, commonly referring to temperature, rainfall and snowfall, wind, and humidity. We have all experienced the changing climate. We do not expect the average summer temperature in Toronto or the yearly average rainfall in Vancouver to be unchanging from year to year, or decade to decade. In the Arctic, the yearly average sea ice cover changes from year to year. So why is there so much attention on climate change?

Changes in climate are due to two factors. The first arises from natural internal processes in the complex interaction among the atmosphere, oceans, sea-ice, land surface, and biosphere. The second comes from external drivers such as volcanic eruptions, solar variations, and human activities that increase the amount of greenhouse gases in the atmosphere.

What does the science show? Analysis of temperature records show pervasive and persistent warming trends at many sites around the world over the past decades. There is more cause for concern. This warming is largely due to our use of fossil fuels and changing land use (such as deforestation), which increase greenhouse gases in the atmosphere.

July 2020 was a sweltering month in Toronto. It was the hottest July on record since Environment and Climate Change Canada began data collection over 80 years ago(1). Toronto was not alone in setting records. Over North America, July 2020 was the second warmest month in 110 years of record, behind 2012. Globally, July 2020 tied with 2016 as the warmest July since records began in 1880(2).

The 2010- 2019 period was the hottest documented decade since 1880; within this decade, 2019 and the five preceding years recorded the highest average annual temperature(3).

The warming is not only pervasive and coming thick and fast, we humans are responsible for much of it! Heat waves, like the one in July 2020 in Toronto, are expected to become more frequent in the future if we do not act now.

What to do? We can adapt to the changing climate, or mitigate the change by reducing our production of greenhouse gases. Given the scale and impact of the expected climate change in the coming years and decades, adaptation efforts alone are not sufficient and mitigation measures must be a crucial part of the solution. An example of adaptation is installing more air conditioning units in senior residences and cooling centers for citizens to deal with increasing incidence of heat waves. Mitigation measures would transition our energy systems away from fossil fuels to zero or low carbon alternatives, and modify our land use practices as well.

There is actually another alternative to adaptation and mitigation to deal with climate change. We can do nothing and suffer the consequences – not a wise choice.

The next time you have a cold drink by the beach or the pool during an unusually hot summer, think about climate change and what you might do about it!


(1) Tom Yun, Toronto Star, July 30, 2020, quoting Dave Phillips of ECCC

(2) NOAA, National Centers for Environmental Information

(3)Katherine Wu, Smithsonian Magazine, January 6, 2020, quoting climate experts from NOAA and NASA

Charles Lin

Charles is a retired atmospheric scientist based in Toronto. He stays busy as founder and lead of ImpactNetZero, keeping healthy in mind and body, and reading stories to his two grandchildren.

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