IT IS possible to keep the increase in global average temperatures to within 1.5 degrees Celsius of pre-industrial times. But for that, the world would need to bring down its greenhouse gas to about half of its 2010 levels by 2030, and to net zero by about 2050, a new report by the Intergovernmental Panel on Climate Change (IPCC) has said.
As of now, the world is striving to prevent the temperature rise beyond 2 degrees Celsius, in accordance with the stated objective of the Paris Agreement of 2015. To meet that target, the aim is to reduce greenhouse gases by only 20 per cent, from 2010 levels, by the year 2030 and achieve a net-zero emission level by the year 2075.
Net-zero is achieved when the total emissions is balanced by the amount of absorption of carbon dioxide through natural sinks like forests, or removal of carbon dioxide from the atmosphere through technological interventions.
In its earlier reports, which have formed the basis of global action, the IPCC has said that climate change could have “irreversible” and “catastrophic” impacts if the global average temperatures were allowed to rise beyond 2 degrees Celsius.
The latest report, released in Seoul Saturday at the end of a week-long meeting, was requested by various countries in 2015 to explore the possibilities of keeping the temperature rise within 1.5 degrees Celsius. This was the key demand made by a number of smaller and poorer countries, especially the small island states, which face the maximum risks from the impact of climate change.
The IPCC, a global body of scientists that makes periodic assessments of science related to climate change to make projections about the future, has presented four pathways through which the 1.5 degree target can be achieved. In each of the pathways, the global average temperature is projected to overshoot the 1.5 degrees Celsius target by some amount before returning to that level before the end of this century.
Each of these pathways is also dependent on some amount of Carbon Dioxide Removal (CDR), a reference to physical removal of the stock of carbon dioxide from the atmosphere to reduce its concentrations.
Technologies for CDR are still undeveloped and untested. Varying amounts between 100 to 1000 gigatons (billion tonnes) of carbon dioxide would need to be removed from the atmosphere in these four pathways, the report says. The world currently emits about 47 billion tonnes of carbon dioxide every year.
“CDR would be used to compensate for residual emissions and, in most cases, achieve net negative emissions to return global warming to 1.5 degrees Celsius following a peak,” the report notes.
The IPCC report says each of these pathways will require “rapid and far-reaching transitions in energy, land, urban and infrastructure (including transport and buildings), and industrial systems”.
The report, which includes contributions from 91 authors and review editors from 40 countries, will be a key scientific input in the upcoming Katowice Climate Change Conference in Poland in December.
“One of the key messages that comes out very strongly from this report is that we are already seeing the consequences of 1 degree Celsius of global warming through more extreme weather, rising sea levels and diminishing Arctic sea ice, among other changes,” said Panmao Zhai, co-chair of IPCC, Working Group I, in a statement.
The report also lists several specific advantages of keeping the global temperature rise within 1.5 degrees celsius from pre-industrial levels.
For example, by 2100, global sea level rise would be 10 cm lower with global warming of 1.5 degrees compared with 2 degrees Celsius. The likelihood of an Arctic Ocean free of sea ice in summer would be once per century with global warming of 1.5 degrees, compared with at least once per decade with 2 degrees Celsius. Coral reefs would decline by 70-90 percent with global warming of 1.5 degrees, whereas virtually all (over 99 per cent) would be lost with 2 degrees Celsius.
In addition, the report also points out that “climate-related risks to health, livelihoods, food security, water supply, human security, and economic growth” are projected to increase with global warming of 1.5 degrees Celsius and increase further with 2 degrees Celsius.
The assessment refers to climate models that project “robust differences in regional climate characteristics” between present-day and global warming of 1.5 degrees Celsius, and between 1.5 and 2 degrees Celsius.
These differences include increase in mean temperatures in both land ocean regions, hot extremes in most inhabited regions, heavy precipitation in several regions, and the probability of drought and precipitation deficits in some regions.