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IPCC Issues Special Report Cautioning Against the Impact of Global Warming Above 1.5 Degrees Celsius

The Intergovernmental Panel on Climate Change (IPCC), a panel of scientists convened by the United Nations, issued a special report on the impact of global warming of 1.5 degrees Celsius above pre-industrial levels (considered as 1850-1900 by the IPCC). The report, published on October 8, 2018 at the conclusion of a panel meeting in South Korea, highlights in dire terms the importance of limiting global warming to 1.5C as compared to 2C. One panel member summarized:


  • Every extra bit of warming matters, especially since warming of 1.5C or higher increases the risk associated with long-lasting or irreversible changes, such as the loss of some ecosystems.

The report concludes that while the 1.5C warming limit can be achieved from a scientific standpoint, doing so will require “rapid and far-reaching” changes that would require unprecedented political and economic cooperation. Global carbon dioxide (CO2) emissions, which are currently rising, would need to fall by 45 percent from 2010 levels by 2030, and would need to reach ‘net zero’ by 2050.



The IPCC, comprised of a body of scientists and economists, was first convened by the United Nations in 1988. It periodically publishes for policy-makers summaries of “the scientific basis of climate change, its impacts and future risks, and options for adaptation and mitigation.” As part of the 2015 Paris Agreement on climate change, in which 195 nations committed to halting global warming to “well below 2C above pre-industrial levels and to pursue efforts to limit temperature increase to 1.5C above pre-industrial levels,” the IPCC was asked to develop this special 2018 report on the impacts of global warming above 1.5 degrees Celsius.

The 2018 report was authored by a team of 91 scientists and policy experts from 44 different countries. The US had the greatest representation with seven authors, followed by Germany with five and the UK by five. The report is the first in a series; next year the panel will publish a report on climate change impacts on the ocean and on land use.


The Implications of 1.5C

At present, global average temperatures have already warmed by approximately 1C since pre-industrial times. However, since the rate of warming is not consistent across the Earth’s surface, some regions representing approximately 20-40 percent of the global population are already experiencing warming of more than 1.5C. As indicated in the report, even at levels of 1.5C severe climate impacts are already playing out on land and ocean ecosystems; the report noted that:


  • Temperature rise to date has already resulted in profound alterations to human and natural systems, bringing increases in some types of extreme weather, droughts, floods, sea level rise and biodiversity loss, and causing unprecedented risks to vulnerable persons and populations.

The areas most impacted will include small islands, coastal regions, areas in poverty, and large cities. These and other areas will face greater extremes in weather conditions with increased rainfall and worsened drought conditions, resulting in flooding and wildfires. The report also states that if warming is limited to 1.5C, coral reefs would decline by 70-90 percent, whereas if 2C is reached, virtually all coral reefs would be lost.


Recommended Courses of Action

To avoid nearing levels of 2C warming, the report identifies a variety of pathways that could limit temperatures to 1.5C, but the pathways envision drastic changes from the status quo, and which may not be politically or economically feasible. For example, one change recommends a fully decarbonized future by 2050, with an electricity mix comprised of 70-85 percent renewable energy. The pathways also envision a 33 percent reduction in methane emissions below 2010 levels by 2050. The transportation and industry sectors are expected to reduce emissions under set pathways to 75-90 percent below 2010 levels by year 2050.

The report also notes that to achieve 1.5C, negative emissions technologies (NETs) will have to be employed to remove CO2 from the atmosphere, and to compensate where emissions cannot easily be reduced to zero (e.g., air travel and food production, particularly meat and rice). Examples of NETs include carbon capture technologies and afforestation (planting trees in barren land).


Conclusion and Implications

If significant corrective actions are not pursued to drastically reduce existing CO2 levels, the IPCC report finds that a warming of 1.5C could be reached in as little as 11 years.

Given the current political climate and President Trump’s statement of intent to withdraw from the Paris Climate Accord, the question remains whether other global, state, or industry players will take the lead in heeding the IPCC report. California’s recently enacted SB 100 sets a path of reaching 100 percent renewable energy supply and a goal of carbon net neutrality by 2045. Its policies may provide a roadmap and help develop the technologies needed to reduce carbon emissions. In addition, some corporations have expressed a preference for carbon taxes or have worked to account for climate changes’ cost to companies. The question remains whether such actions and interests can be implemented quickly enough to avoid the dire consequences listed in the IPCC report. See related scientific detailed coverage of this event on page 1234567890987654321of this issue of the Climate Change Law & Policy Reporter.

(Lilly McKenna)