A changing climate is no doubt the current challenge faced by the global community. From heat waves to floods that wipe out residential areas, this is an undeniable reality owing to years of unsustainable developmental practices. To ensure that world policy makers are equipped with periodical scientific assessments of climate change, its consequences, and potential future hazards as well as to propose adaptation and mitigation strategies, The Intergovernmental Panel on Climate Change (IPCC) was established as an intergovernmental body of the United Nations.
In line with the responsibility of assessing the science related to climate change, IPCC released its Sixth Assessment Report (AR6) publication, Climate Change 2021: The Physical Science Basis on the 9th of August 2021. This report gives an in-depth insight on current climate science, encompassing how the climate is changing and the role of human impact, the state of knowledge about probable climatic futures, climate data relevant to regions and different sectors, and advocates for controlling human-induced climate change. Employing the use of advances in climate science, such as “new climate model simulations, new analyses, and methods combining multiple lines of evidence”, estimates are provided in this report on the above mentioned areas.
Current State of the Climate:
According to the report, human activities have continued to champion the cause of global warming.
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.
Human activities have been implicated in the observed increases in well-mixed greenhouse gas (GHG) concentrations since the 1750s. Since 2011, carbon dioxide (CO2), methane (CH4), and nitrous oxide (N2O) concentrations in the atmosphere have continued to rise, with annual averages of 410 ppm for CO2, 1866 ppb for CH4, and 332 ppb for N2O in 2019. Since 1850, each of the previous four decades has been gradually warmer than the decade before it.
The report states that
The scale of recent changes across the climate system as a whole and the present state of many aspects of the climate system are unprecedented over many centuries to many thousands of years.
Many weather and climatic extremes are already being influenced by human-caused climate change in every part of the world. Since AR5 (Fifth Assessment Report), the evidence of observed changes in extremes including; heat-waves, heavy precipitation, droughts, and tropical cyclones, and in particular, their attribution to human impact, has grown stronger.
Possible Climate Futures
Warning the global community about predicted climate futures, the report revealed that
Global surface temperature will continue to increase until at least the mid-century under all emissions scenarios considered. Global warming of 1.5°C and 2°C will be exceeded during the 21st century unless deep reductions in CO2 and other greenhouse gas emissions occur in the coming decades. Many changes in the climate system become larger in direct relation to increasing global warming. They include increases in the frequency and intensity of hot extremes, marine heat-waves, and heavy precipitation, agricultural and ecological droughts in some regions, and proportion of intense tropical cyclones, as well as reductions in Arctic sea ice, snow cover and permafrost.
Facts for concern were the certainty that the land surface will very certainly continue to warm faster than the water surface (likely 1.4 to 1.7 times more). The Arctic will also very certainly continue to warm faster than the world surface temperature, with a strong probability of exceeding two times the pace of global warming. The global water cycle and its unpredictability, worldwide monsoon precipitation, and the intensity of wet and dry episodes, are expected to become more intense as a result of continued global warming. A warmer climate would amplify extreme wet and dry weather, climatic events, and seasons, perhaps resulting in floods or drought.
Future possible implications of climate change in the report also indicates that
Under scenarios with increasing CO2 emissions, the ocean and land carbon sinks are projected to be less effective at slowing the accumulation of CO2 in the atmosphere. Many changes due to past and future greenhouse gas emissions are irreversible for centuries to millennia, especially changes in the ocean, ice sheets and global sea level.
Climate Information for Risk Assessment and Regional Adaptation
In communicating risk assessment, the report warns that
Natural drivers and internal variability will modulate human-caused changes, especially at regional scales and in the near term, with little effect on centennial global warming. These modulations are important to consider in planning for the full range of possible changes.
Internal variability will either amplify or reduce projected human-caused changes in mean climate and climatic impact-drivers (CIDs), including extremes.
With further global warming, every region is projected to increasingly experience concurrent and multiple changes in climatic impact-drivers. Changes in several climatic impact-drivers would be more widespread at 2°C compared to 1.5°C global warming and even more widespread and/or pronounced for higher warming levels.
Limiting Future Climate Change
According to the report’s 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.
The report concludes that the global CO2-induced surface temperature increase would be progressively reversed if worldwide net negative CO2 emissions were achieved and maintained, but other climatic changes would continue in their current path for decades to millennia. Even with huge net negative CO2 emissions, it would take several centuries to millennia for global mean sea level to reverse direction. Thus, CO2 emissions from the past, present, and future bind the globe to significant multi-century climate change, and many aspects of climate change would remain for millennia even if CO2 emissions were immediately halted.
Summarily, this report gives a clear insight o the fact that reduced CO2 emissions are insufficient to mitigate the harmful effects of climate change. Air quality improvements and a reduction in global warming are anticipated to result from merged efforts of targeted air pollutant emissions and GHG emissions reductions, which poses beneficial effects on both the climate and human health. This places a huge burden on the scale of work and commitment left to be done by the global community.
This report can be accessed using the link below:
IPCC, Sixth Assessment Report, Climate Change 2021: The Physical Science Basis, SPM-5, viewed on 10 August 2021, https://www.ipcc.ch/report/ar6/wg1/downloads/report/IPCC_AR6_WGI_Full_Report.pdf
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