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The IPCC sixth assessment report strives to cover different aspects of climate change and provides a holistic view of the developments related to climate change. It assesses new scientific evidence relevant for a world whose climate system is rapidly changing, overwhelmingly due to human influence.

As the global warming levels get progressively higher, there are going to be greater consequences for the planet and its people. There has been substantial progress made in combining new evidence of Earth’s climate sensitivity with improvements in the understanding and quantification of Earth’s energy imbalance. The near-linear relationship between cumulative CO2 emissions and maximum global surface temperature increase caused by CO2 emissions and maximum global surface temperature implies that at any level net anthropogenic CO2 emissions need to become zero.

An Uphill Battle

Achieving the set target of net-zero, however, is an uphill battle. Limiting further climate change would require substantial and sustained reductions in GHG emissions. This means that considerable changes would have to be brought about in human activities and planned interventions.

While there are several causes for rising emissions, it is unequivocal that human influence has warmed the atmosphere, ocean, and land. Widespread and rapid changes in the atmosphere, ocean, cryosphere, and biosphere have occurred. Each of the last four decades has been successively warmer than any decade that preceded it since 1850. The likely range of human-caused global surface temperature increase from 1850-1900 to 2010-19 is around 0.8 degrees Celsius.

From a physical science perspective, limiting human-induced global warming to a specific level requires limiting cumulative CO2 emissions, reaching at least net-zero CO2 emissions, along with strong reductions in other greenhouse gas emissions.  Strong, rapid, and sustained reductions in CH4 emissions would also limit the warming effect resulting from declining aerosol pollution and would improve air quality.  Given the estimates presented in the report, every step taken towards climate targets is crucial and every effort would be critical in determining the future of our planet.

Is the Damage Done?

Human-induced climate change is already affecting many weather and climate extremes in every region across the globe. Evidence of observed changes in extremes such as heatwaves, heavy precipitation, droughts, and tropical cyclones, and, in particular, their attribution to human influence has strengthened since IPCC’s fifth assessment report. Many changes due to past and future greenhouse gas emissions are irreversible for centuries to millennia, especially changes in the oceans, ice sheets, and global sea levels. Continued global warming is projected to further intensify the global water cycle, including its variability, global monsoon precipitation, and the severity of wet and dry events.

The scale of recent changes across the climate system as a whole presents the state of climate change aspects that are unprecedented over many centuries.  The report predicts an estimate of equilibrium climate sensitivity of 3 degrees Celsius, with a narrower range compared to AR5. Also, with further global warming, every region is projected to increasingly experience concurrent and multiple changes in climate impact. It further predicts that given these contrasting scenarios, discernible differences in trends of global surface temperature would begin to emerge from natural variability within around 20 years or maybe longer.

About The Author

Srishti Tiku

Srishti is a graduate in Behavioral Economic Science from University of Warwick, UK, and is passionate about using her knowledge to decipher sustainability challenges through research and analysis. As Economics attempts to explain the processes that shape lives and livelihoods, Srishti finds it fascinating to learn about emerging patterns while wading her way through issues engulfing people, planet and profit. When she is not at desk, she loves to read and watch movies.

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