Climate Change from past to contemporary
- November 3, 2021
- Posted by: OptimizeIAS Team
- Category: DPN Topics
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Climate Change from past to contemporary
Subject – Environment
Context – CoP26: Humanity is compressing millions of years of natural change into just a few centuries
Concept –
- According to IPCC report, global temperature (currently 1.1℃ above a pre-industrial baseline) is higher than at any time in at least the past 120,000 or so years.
- That’s because the last warm period between ice ages peaked about 125,000 years ago – in contrast to today, warmth at that time was driven not by CO2, but by changes in Earth’s orbit and spin axis.
- Another finding regards the rate of current warming, which is faster than at any time in the past 2,000 years – and probably much longer.
- The current atmospheric CO2 concentration of around 415 parts per million (compared to 280 ppm prior to industrialisation in the early 1800s), is greater than at any time in at least the past 2 million years.
An IPCC graphic showing climate changes at various points since 56 million years ago. Note most rows show changes over thousands or millions of years, while the top row (recent changes) is just a few decades.
- Other climate variables can also be compared to past changes.
- These include the greenhouse gases methane and nitrous oxide (now greater than at any time in at least 800,000 years),
- late summer Arctic sea ice area (smaller than at any time in at least the past 1,000 years),
- glacier retreat (unprecedented in at least 2,000 years)
- sea level (rising faster than at any point in at least 3,000 years),
- ocean acidity (unusually acidic compared to the past 2 million years).
- An “intermediate” amount of emissions will likely lead to global warming of between 2.3°C and 4.6°C by the year 2300, which is similar to the mid-Pliocene warm period of about 3.2 million years ago.
- Extremely high emissions would lead to warming of somewhere between 6.6°C and 14.1°C, which just overlaps with the warmest period since the demise of the dinosaurs — the “Paleocene-Eocene Thermal Maximum” kicked off by massive volcanic eruptions about 55 million years ago.
- “Climate sensitivity” — the amount it warms when atmospheric CO2 is doubled.