Depending on global economic trends, technological progress, and geopolitical developments, the most important thing is that we act now to reduce carbon emissions before the world turns out to be very different at the end of the twenty-first century.
Physical Science of Climate Change was published last week. The report contains five climate reports, which differ in terms of the extent of projected warming and the ability of societies to adapt to change.
In an IPCC report published last week, different levels of emissions under different scenarios driven by various degrees of warming in climate models lead to a range of physical impacts on the world.
The implications of these different socio-economic strands of action will become more relevant in the second and third chapters of the new IPCC report, due to be published in 2022. Climate protection depends on scenarios, and each design represents different attitudes and technological advances. Climate scientist and IPCC co-author Jessica Tierney of the University of Phoenix looks at the report.
In their fifth assessment report, published in 2013 and 2014, the modelers used a series of representative concentration paths (RCPs) to project our climate future. Its authors have chosen to present a wide range of stories to help politicians and the public understand the choices ahead and what is at stake if we do not make intelligent choices.
The RCP scenarios differ due to humanity’s efforts to mitigate climate change, ranging from high emission reductions (scenario RCP 2.6 with low emissions) to high emission reductions (scenario RCP 8.5). Some of the following scenarios indicate radiation propulsion or how much additional energy our emissions to the Earth system will add (measured in watts per square meter) by 2100. As the Earth receives more power from radiant forces, the temperature will rise.
The scenarios underlying the Sixth Assessment Report contain additional human elements that make their decoding somewhat more complex. The IPCC’s sixth assessment report includes a radiant power scenario of 2.6-4.5 watts per square meter and a high-end scenario of 7 watts / square meter.
The anatomy of a climate scenario
The most significant change in the new report is that emission paths are not alone. They were paired with the shared socio-economic development scenarios of the twenty-first century. It forecasts how population, economic growth, technological and geopolitical trends will affect emissions and our ability to reduce emissions and adapt to climate change they cause.
Global emissions will reach net zero by the mid-to-late twenty-first century (or sink into negative territory). Humanity will begin to capture vast amounts of carbon dioxide from the air by using technologies that have yet to be proven on a large scale.
By the end of the century, the Earth is warming by 2.5 degrees Celsius (1.4 degrees Celsius) in the first optimistic scenario and 3.2 degrees Celsius (1.8 degrees Celsius) in the second.
The good, the bad, and the weird
Carbon emissions would remain high until the middle of the century before declining. Hausfather says this scenario aligns with the nation’s “2030 climate commitments under the Paris Agreement. By the end of this century, the world would be warming between 4.9 and 2.7 degrees Celsius.
It is a future that corresponds to historical patterns of socio-economic development. Medium-term history provides for global economic growth, with some countries on the path to greater prosperity and social equality while others are falling behind. Fertility rates in developing countries remain high, and the world’s population will peak at 9.5 billion by the end of the century.
Tail-end outcomes: unlikely but important
In many of the world’s impoverished countries, birth rates remain high, leading the world’s population to rise from 1.2 billion at the end of this century to about 8 billion. Today, many parts of the world are still vulnerable to severe climate impacts. Economic growth and social progress are faltering. Global cooperation is collapsing in the IPCCs, and nationalism is gaining influence in some countries. Show Source Texts
Carbon emissions will continue to rise this century, leading to global temperatures reaching a whopping 3.5 degrees Celsius above pre-industrial levels by 2100. Droughts and floods will worsen, summer Arctic sea ice will disappear within 50 years, and heatwaves will occur 40% of the time.
In such a world, humanity would not only fail to reverse its emissions curve, but it would also double fossil-fuel extraction and an energy-intensive lifestyle. If nations dug up and burned more coal this century, the world would warm to an unimaginable 4.4 degrees Celsius, hotter than it has been for millions of years.
Hausfather points out that nations, which account for two-thirds of global emissions, have already committed to reducing emissions to zero by the middle of this century. If they can deliver on that promise, and if other developed countries follow suit (there are some big ifs and buts, of course), it would put a warming outcome of between 1.5 and 2 degrees on the table. We chose the better way, “he says.