5 Takeaways From the U.N. Climate Report
On Monday, the Intergovernmental Panel on Climate Change, a scientific body convened by the United Nations, released a major new report concluding that the world cannot avoid some devastating effects of climate change, but there are still has a narrow window to prevent the devastation from getting even worse.
The report, based on the analysis of more than 14,000 studies, is the clearest and most comprehensive summary of the physical science of climate change to date. It describes what the climate looked like in the past, what it looks like now, and what it will look like in the decades to come. And it shows how humans can affect the future climate through actions they take – or don’t take – now to reduce emissions of carbon dioxide and other heat-trapping gases.
Here are five takeaways from the report:
Human influence has unequivocally warmed the planet.
This report is the sixth climate science assessment by the United Nations group, and unlike previous reports, this one eliminates any doubt about who or what is responsible for global warming. “It is unequivocal that human influence has warmed the atmosphere, the oceans and the land,” the report states in its very first conclusion.
The observed increases in carbon dioxide in the atmosphere since 1750 may be directly related to human activity, largely the burning of coal, oil, and other fossil fuels as the world industrialized. These emissions have increased dramatically over time and continue today as the world warms even more. And the impacts are being felt in all regions of the world.
Climate science is improving and becoming more precise.
One of the reasons the report can conclude without a doubt that humans are responsible for global warming is that climate research has improved dramatically, even in the eight years since the publication of the previous report of the ‘UN.
There is much more observational data – temperature measurements and other data from instruments on land, in the oceans and in space – that reduces the uncertainty about what is happening. The improvement is particularly visible in some less affluent regions of the world that historically had little capacity to collect climate data.
Computer models that simulate the climate have also improved dramatically, and there is more computational power to run these simulations faster so they can be repeated over and over again. These improvements, along with the ability to fit more and better data into models, give scientists more confidence that their models correctly predict future climate.
Over the past decade, great strides have been made in attribution research, which seeks to examine possible links between climate change and specific extreme events such as heat waves and heavy rains. Research teams can now quickly analyze an event and determine whether warming has made it more or less likely to occur, thus boosting global confidence in the nature of climate change.
We are locked in 30 years of worsening climate impacts no matter what the world does.
The world has already warmed by around 1.1 degrees Celsius (about 2 degrees Fahrenheit) since the 19th century. The report concludes that humans have emitted so much carbon dioxide and other greenhouse gases into the atmosphere that this warming will continue at least until the middle of the century, even if nations take immediate action today. hui to greatly reduce emissions.
This means that some of the notable effects the world is currently experiencing – such as extreme droughts, severe heat waves, and catastrophic showers and floods – will continue to worsen for at least the next 30 years.
Some other impacts will continue for much longer. The enormous ice caps of Greenland and West Antarctica will continue to melt at least until the end of the century. Global sea level will continue to rise for at least 2,000 years.
Climate change is happening fast.
The report found that some of the changes are more significant than they have ever been compared to previous periods ranging from centuries to several millennia.
The concentration of carbon dioxide in the atmosphere, for example, is higher than at any time in the past two million years. The extent of late summer ice in the Arctic is smaller than it has ever been in the past 1,000 years.
But the report also found that changes are happening faster now than even in the much more recent past. The rate of sea level rise has practically doubled since 2006. Each of the past four decades has been successively warmer than the last. Heat waves on land have become much hotter since 1950, and marine heat waves – surges of extreme heat in the ocean that can kill marine life – have doubled in frequency over the past four decades.
There is still a window in which humans can alter the climate trajectory.
The report presents five climate futures, in which humans take various actions to reduce emissions that cause warming. In each of them, the world will reach 1.5 degrees – the most ambitious of the targets set by the Paris agreement on climate change in 2015 – by 2040 or sooner.
In most of the scenarios discussed in the report, warming will continue well beyond 2040, until the end of the century. In the worst cases, where the world is doing little to reduce emissions, temperatures by 2100 could be 3 to 6 degrees Celsius (5.5 to 11 degrees Fahrenheit) above pre-industrial levels. It would have catastrophic consequences.
But the report shows that aggressive, rapid and widespread emission reductions, from now on, could limit warming beyond 2050. In the most optimistic scenario, reaching “net zero” could even bring warming back slightly. less than 1.5 degrees Celsius during the second half of the century.
Such a scenario would be a gigantic and costly undertaking for the world. It would also require a level of political will that most governments have so far failed to muster.
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