Five things we have learned from the IPCC report

US President Donald Trump has questioned the science of manmade climate change and vowed to withdraw the US, the world’s second largest emitter of greenhouse gases after China, from the agreement.

The new report says we’ll see those effects in just over 20 years unless major changes are implemented.

The Paris accord was signed three years ago by nearly 200 nations, who pledged to keep warming to 1.5-2 degrees. Paris was itself based on the former 2 degree Celsius threshold.

The shares of nuclear and fossil fuels with carbon dioxide capture and storage in electricity generation are modelled to increase in most 1.5-degree pathways “with no or limited overshoot”.

While businesses, sub-national governments and many countries have committed to climate action, and achieved some progress – see the $9 trillion We’re Still In Campaign – slow movement from those that profit off fossil fuels and staunch resistance from parties like the Trump administration have made collective action hard.

“This is concerning because we know there are so many more problems if we exceed 1.5 degrees C global warming, including more heat waves and hot summers, greater sea level rise, and, for many parts of the world, worse droughts and rainfall extremes”, Andrew King, a climate science academic at the University of Melbourne, said in a statement to CNN. Therefore, even though urgent action is a necessity, it should be equitable and the onus of addressing climate change can not fall on the developing world. In what IPCC chair Hoesung Lee, a South Korean economist, called “a Herculean effort”, more than 90 authors and reviewers from 40 countries examined 6,000 scientific publications.

In the 728-page document, the United Nations organization detailed how Earth’s weather, health and ecosystems would be in better shape if the world’s leaders could somehow limit future human-caused warming to just 0.9 degrees Fahrenheit (a half degree Celsius) from now, instead of the globally agreed-upon goal of 1.8 degrees F (1 degree C). It also recommends improving irrigation efficiency, the expansion of electric vehicles, the adaptation of “smart grid” electrical systems, improving the efficiency of food production, and even dietary choices which give off lower emissions (beef, in particular, has a large carbon footprint). “It is crucial to keep temperature rise well below 1.5 degrees without offsetting, carbon markets, and geoengineering, but the evidence presented by the IPCC shows that there is a narrow and shrinking window in which to do so”. Doing so would certainly require massive investments, but they would pay off.

The pledges nations made in the Paris agreement in 2015 are “clearly insufficient to limit warming to 1.5 in any way”, one of the study’s lead authors, Joerj Roeglj of the Imperial College in London, said. The not-so-great news? They need to accelerate. We also will need to rely on carbon removal-whether that’s as low-tech as planting trees or using new technology like direct air capture that can suck CO2 from the atmosphere. “Denying the reality of climate change is not going to help anyone”. “Net CO2 emissions at the global scale must reach zero by 2050”, said Valerie Masson-Delmotte, a climate scientist at France’s Alternative Energies and Atomic Energy Commission in Paris and a key participant in drafting the report.

She said: “Currently renewables are backed up by gas when they are not generating and, in the United Kingdom, gas is backed up by coal”.

The report contrasts the impact of 1.5℃ and 2℃ warmings, giving information on what would be gained by the extra effort needed to limit warming to 1.5℃.

The IPPC report represents “sobering assessment of the challenge we face, and of the risks and costs of a warming planet”, Caroline Theriault, a spokeswoman for Environment Minister Catherine McKenna, said.

While the difference between 1.5 deg C and 2 deg C might seem small, some types of climate-change impact will be less severe by limiting global warming.

The report notes that we are now at a warming of about 1.0°C, with the warming trend rolling along at 0.2±0.1°C per decade.

Still, Cleetus says that we have most of the technology we need to make the change. To hit and keep that 1.5 degrees target, net anthropogenic Carbon dioxide emissions must come down 45% from 2010 levels by 2030 and reach net zero around 2050.