Countries have to make unprecedented transitions in all sectors to avoid devastating consequences of climate change and keep global warming within 1.5 degrees Celsius above pre-industrial levels this century, says a report by Intergovernmental Panel on Climate Change (IPCC), an worldwide body set up in 1988.
Although the report says that emissions would not be the sole contributor to temperatures above 1.5°C, the future rates of emission reductions will determine whether temps rise.
"I can give you reports that are fabulous and I can give you reports that aren't so good", Trump said. Human-produced Carbon dioxide emissions would have to drop by 45 percent from 2010 levels by 2030, reaching "net zero" by 2050, according to the report. However, the world has already warmed about 1 deg C since pre-industrial times. "These cuts are the fastest way to slow down warming while we decarbonize the energy system and learn how to remove carbon from the atmosphere at the scale we need".
How much more urgent can it get?" and "Science pronounces its verdict: "World to be doomed at 2°C, less unsafe at 1.5°C" and "A major new climate report slams the door on wishful thinking".
"I just don't see the possibility of doing the one and a half" and even 2 degrees looks unlikely, said Appalachian State University environmental scientist Gregg Marland, who isn't part of the United Nations panel but has tracked global emissions for decades for the U.S. Energy Department.
This means no more Carbon dioxide should be put out than is being removed by current measures, such as planting trees.
"Every extra bit of warming matters, especially since warming of 1.5°C or higher increases the risk associated with long-lasting or irreversible changes, such as the loss of some ecosystems", Co-Chair of IPCC Working Group II Hans-Otto Pörtner said.
World Wildlife Fund Australia campaigner Monica Richter said food waste is one area where consumer decisions can make an impact on global warming.
"The next few years are probably the most important in our history", said Debra Roberts, an IPCC co-chair.
This one-two punch poses a powerful call to action: maybe the combination of messages can motivate change where the consensus of 97% of global climate change research scientists has failed to achieve action in line with the Paris Accord.
Greenpeace East Asia climate and energy campaigner Walton Li said Hong Kong possessed one of the largest carbon footprints in the world and had a responsibility to "radically" revise its emissions strategy.
"There were doubts if we would be able to differentiate impacts set at 1.5°C and that came so clearly".
The IPCC study, which took almost three years to complete and involved 91 authors from 40 countries, is the first to look in detail at the 1.5 deg C limit, which is one of the goals in the 2015 UN Paris Climate Agreement.
Developing nations and least developed countries have been asking developed nations, particularly the United States, to take historical and moral responsibility for being one of the largest greenhouse gas emitters.
The report warned that half a degree increase in global warming temperature is a big deal and can have catastrophic consequences which will be there for people to see in their current lifetimes.
Science shows that nothing does more to cause climate change than burning coal, a former head of the US Environmental Protection Agency (EPA) said on Tuesday, a position in contrast to President Donald Trump's pro-fossil fuel policies. "There's certainly things that we'll need to invest in more to develop the next generation of solutions".
That could reduce flooding and give the people that inhabit the world's coasts, islands and river deltas time to adapt to climate change.