A landmark United Nations report on Monday warned that sufficiently limiting man-made global warming will “require rapid, far-reaching and unprecedented changes in all aspects of society” in order to avoid dramatic global consequences, including rising sea levels, dying coral reefs and human casualties due to extreme heat.
The special report — published Monday by the United Nations’ Intergovernmental Panel on Climate Change — assessed what it will take to limit global temperature increase to no more than 2.7º F (1.5º C) above preindustrial levels, in accordance with the 2015 Paris Agreement. Scientists consider that temperature to be a tipping point at which many severe effects of global warming will be realized.
“Examples of actions include shifting to low- or zero-emission power generation, such as renewables; changing food systems, such as diet changes away from land-intensive animal products; electrifying transport and developing ‘green infrastructure’, such as building green roofs, or improving energy efficiency by smart urban planning, which will change the layout of many cities,” the report said.
The report called climate change “an urgent and potentially irreversible threat to human societies and the planet,” and warned that delayed action would make it impossible to limit warming to 2.7º F.
“While the pace of change that would be required to limit warming to [2.7º F] can be found in the past, there is no historical precedent for the scale of the necessary transitions, in particular in a socially and economically sustainable way,” the report stated. “Resolving such speed and scale issues would require people’s support, public-sector interventions and private-sector cooperation.”
Here are some of the changes that will need to be made in order to stop the current pace of global warming:
Reduce carbon emissions by 45%
By 2030, global carbon dioxide emissions must be 45% less than they were in 2010, the report found. And carbon dioxide emissions must reach net zero around 2075 — meaning the amount of carbon dioxide entering the atmosphere equals the amount being removed.
By 2050, emissions of other heat-trapping greenhouse gasses, including methane and black carbon, should be reduced by 35%, relative to the 2010 rate.
“Emissions would need to decline rapidly across all of society’s main sectors, including buildings, industry, transport, energy, and agriculture, forestry and other land use,” the report said.
The United States — which has contributed more to carbon pollution than any other country in history — emitted 5.6 billion metric tons of carbon dioxide in 2010, according to the U.S. Energy Information Administration. If the United States followed the report’s 45% goal, it would have 12 years to decrease annual emissions by more than 2.5 billion metric tons.
In 2017, global energy-related carbon emissions rose to a record high.
Scrub carbon dioxide from the air
In addition to reducing carbon dioxide emissions, the report recommended carbon dioxide removal measures — including planting new trees and carbon capture and storage, a process by which carbon dioxide is trapped and prevented from entering the atmosphere.
“Most current and potential [carbon dioxide removal] measures could have significant impacts on land, energy, water, or nutrients if deployed at large scale,” the report said.
Use 85% renewable energy and stop using coal entirely
The report recommended far-reaching changes to land use, urban planning, infrastructure systems and energy use — changes that will be “unprecedented in terms of scale.”
Climate scientists said renewable energy sources will have to account for 70% to 85% of electricity production by 2050. The use of coal should decrease steeply and should account for close to 0% of global electricity, and gas just 8%.
“While acknowledging the challenges, and differences between the options and national circumstances, political, economic, social and technical feasibility of solar energy, wind energy and electricity storage technologies have substantially improved over the past few years,” the report stated. “These improvements signal a potential system transition in electricity generation.”
Plant new forests equal to the size of Canada
Scientists recommend that up to about 3 million square miles of pasture and up to 1.9 million square miles of non-pasture agricultural land be converted into up to 2.7 million square miles for energy crops, which can be used to make biofuels. That would amount to land a little less than the size of Australia.
The report also recommends adding 3.9 million square miles of forests by 2050, relative to 2010 — which is roughly the size of Canada.
“Such large transitions pose profound challenges for sustainable management of the various demands on land for human settlements, food, livestock feed, fibre, bioenergy, carbon storage, biodiversity and other ecosystem services,” the report stated. “Mitigation options limiting the demand for land include sustainable intensification of land use practices, ecosystem restoration and changes towards less resource-intensive diets.”
Correction: Oct. 9
The original version of this story misstated the size of additional forest that must be planted, according to a U.N. Intergovernmental Panel on Climate Change report. It is 3.9 million square miles, not 3.9 square miles.