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Climate Change: a brief on the history and status today

May 03, 2024 / 17:19 IST
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You’d be wrong to think that the keyword in climate change was “change”. It’s “climate” and that frames the enormity of the problem. High school geography taught us that weather is a local phenomenon that can swing in a matter of hours. A city could be sweltering hot in the morning but a hefty afternoon shower will cool things down to the point that it feels like a different place altogether.

On a larger scale the cycling of weather changes through the year is what brings about the seasons. The timely switchover is essential to the way we live and our crop cycles. But to change something as complex and overarching as the planet’s climate system itself is a testament to the influence we exert over our surroundings. The two aspects to this – what we have done and what we can do – have been exploited to muddle the conversation.

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The earth’s climate has shifted dramatically several times in the past but that happened before human existence. During the Cambrian era (~500 million years ago) the earth had multiple active volcanoes and with an atmospheric CO2 concentration of roughly 4000 parts per million (ppm), the average ambient temperature could have hovered around 49° Celsius. For context, the average temperature today is more than a third lower at 15° Celsius. This isn’t surprising as the excess CO2 trapped a lot more of the infrared radiation beamed back from the earth at a longer wavelength. The last Ice Age on the other hand lasted from roughly 115,000 to 11,700 years ago when much of the world was buried under metres of ice. It is hypothesised that a series of meteor showers during the Younger Dryas years broke the gridlock and warmed the planet into the Holocene era we’re living through today.

Humans had little impact on atmospheric CO2 till the industrial revolution. From the mid-1800s the proliferation of industry, the IC engine and the use of fossil fuels to generate power led to a sharp increase in CO2 emissions. At the moment atmospheric CO2 stands at just over 424 ppm – the highest ever in recorded human history. It’s not coincidental that 2023 was the warmest year on record (2024 could be worse), that wildfires and cyclones have shot up in frequency and that rising sea levels will swallow entire island nations.