You can’t un-feel it or un-think it; you certainly can’t un-live it. The special report on “Global Warming of 1.5 degrees C,” from the Intergovernmental Panel on Climate Change (IPCC), released on October 8 in South Korea, issued probably the final warning for the world in stark terms:  Human activity has caused one 1.1C of global warming above pre-industrial levels. It is likely to reach 1.5C between 2030 and 2052, if greenhouse gas emissions continue as at present.

At present, “Warming greater than the global annual average is being experienced in many land regions and seasons, including two to three times higher in the Arctic. Warming is generally higher over land than over the ocean,” according to the 33-page Summary for Policymakers.

(The report’s full name is Global Warming of 1.5°C, an IPCC special report on the impacts of global warming of 1.5°C above pre-industrial levels and related global greenhouse gas emission pathways, in the context of strengthening the global response to the threat of climate change, sustainable development, and efforts to eradicate poverty.)

Based on 6,000 scientific studies and written by 91 authors and review editors from 40 countries, the report from the IPCC—a body of scientists and economists that informs climate polices of the UN member states, established by the UN Environment Programme and the World Meteorological Organization (WMO) in 1988—focuses on and quantifies  the differences in impacts between 1.5C and 2C warming. Many of the effects that were thought to occur at the rise of 2C would, according to the report, occur at 1.5C.

Limiting warming to 1.5C above pre-industrial levels requires wholesale changes in energy systems, transportation, land use, cities, and industry.

The report was issued at the urging of small island states and vulnerable countries. The piercing scream can’t be heard from underwater, which is where these islands will be if the waters rise. The previous consensus said 2 degrees would be a safe limit—industrialised countries manipulated it that way—beyond which lay catastrophe. The Paris Climate Change Agreement, hashed out in 2015, set a goal of “holding the increase in the global average temperature to well below 2C (3.6F) above pre-industrial levels and pursuing efforts to limit the temperature increase to 1.5C (2.7F).”

Now it is said that a 2C rise in average temperatures and the consequent rise in sea levels will threaten the existence of island states like the Maldives, Mauritius, and the Marshall Islands in a few years. The Alliance of Small Island States insisted that the IPCC prepare a special report detailing the specific effects of a 1.5 degree rise and ways to keep it at that level. (As an aside, pledges made by countries in the Paris Agreement would lead to a 3C rise by the end of the century.)

Limiting warming to 1.5C above pre-industrial levels would call for “rapid, far-reaching and unprecedented changes in all aspects of society.” It requires wholesale changes in energy systems, transportation, land use, cities, and industry. In short, we have to reconsider every aspect of our lives at an individual and collective level. It is perhaps the only way to get close to the drastic cut in carbon emissions that are called for to avoid this catastrophe. 

It’s not just the magnitude of change occurring in climate, oceans, and land, but also the pace of change, according to the report. In the last ten years, the world has witnessed deadly heat waves, intense storms, droughts and forest fires, on the back of 1C warming. It can only get worse at 1.5C. No one now is willing to wager what might happen at 2 degrees.

Secondly, the report focuses on the carbon budget. Carbon dioxide accumulates and lingers in the atmosphere for centuries. This leads to warming.

The carbon budget, according to the U.K-based climate and energy news website Carbon Brief, is “a simplified way to measure the additional emissions that can enter the atmosphere, if the world wishes to limit global warming to levels such as 1.5C.”  This quantity is referred to as the carbon budget for 1.5C.  Global carbon dioxide emissions from all human activities (fossil fuels, industry and land-use change) is estimated at around 41 billion tonnes (in 2017), according to the Global Carbon Project (GCP), a research project that relates the knowledge of greenhouse gases from human activities to the earth system. GCP estimated India’s emissions to grow by two per cent (in 2017), compared to six per cent averaged over the previous decade.



part from carbon, other greenhouse gases, in particular, methane (CH4), nitrous oxide (N2O), and halogenated compounds (mainly CFCs), contribute to warming.

According to the US National Oceanic and Atomospheric Organization’s (NOAA) Annual Gas Index, updated in 2018, the growth rate of methane declined from 1983 until 1999, and remained constant. But since 2007, globally averaged methane has been increasing again. Causes for the increase during 2007-2008 included warm temperatures in the Arctic in 2007 and increased precipitation in the tropics in 2007 and 2008.

The Index reports that, since 2013, the global within-year increase (1 Jan to 1 Jan) in methane has become even larger, with increases between 8.8 ± 2.6 through 2017 compared to an average annual increase of 5.7 ± 1.1 parts per billion year (ppb) between 2007 and 2013.

The atmospheric burden of nitrous oxide continues to increase slowly with an average rate of 0.9 ppb over the past decade.

The burden of chlorofluorocarbons (CFCs) continues to decline due to the Montreal Protocol on Substances that Deplete the Ozone Layer, a 1987 treaty for protecting the ozone layer.

According to the US Environmental Protection Agency, methane concentrations have more than doubled since pre-industrial times, reaching approximately 1,800 ppb in 2015. This is due to agriculture and fossil fuel use. Nitrous oxide rarely exceeded 280 ppb in the last 800,000 years. But since the 1920s, it has risen to a high of 328 ppb in 2015.

The report says we have only 11 years before we blow past the carbon budget, even if the current pledges on emission cuts are fulfilled.

According to a 2018 study in Nature Communications, the IPCC has not counted the methane release from the abrupt thawing of permafrost, in contrast to the gradual thaw of near-surface in the thermokarst lakes in the Arctic and Siberia. About 1,500 billion tonnes of carbon is stored deep in the permafrost. The abrupt thaw alone “accelerates mobilisation of deeply frozen, ancient carbon, increasing C-depleted permafrost soil carbon emissions by ~125–190 per cent compared to gradual thaw.” The study suggests that this is going to be a huge problem even if carbon emissions drop significantly.

The IPCC report says we have only 11 years before we blow past the carbon budget, even if the current pledges on emission cuts are fulfilled.

Thirdly, a half-degree rise could flip systems beyond any chance of recovery. The report, for the most part, compares the changes that would occur at 1.5 degrees and 2 degrees.  But on the road to half-a-degree rise from the present, things look calamitous.

According to the summary, “the assessment that an additional 0.5C of warming compared to present is associated with further detectable changes in these extremes.”

Regionally, with global warming up to 1.5C compared to preindustrial levels, there will be  warming of extreme temperatures in many regions, increases in frequency, intensity, and/or amount of heavy precipitation in several regions , and an increase in intensity or frequency of droughts in some regions.”

There will be temperature extremes on land, warmer than the Global Mean Surface Temperature (GMST). There will be extreme hot days in mid-latitudes, warming as much as 3 degrees at global warming of 1.5C. The report projects risks from drought and longer dry spells.



eas will continue to rise well beyond 2100 even if global warming is limited to 1.5C in the 21st century. Marine ice sheet instability in Antarctica and/or irreversible loss of the Greenland ice sheet could result in multi-metre rise in sea levels over hundreds to thousands of years. These instabilities could be triggered around 1.5C to 2C of global warming. Biodiversity and ecosystems, including species loss and extinction, will be massively affected.

“Of 105,000 species studied, 96 per cent of insects, 8 per cent of plants and 4 per cent of vertebrates are projected to lose over half of their climatically determined geographic range for global warming of 1.5 degrees C, compared with 18 per cent of insects, 16 per cent of plants and 8 per cent of vertebrates for global warming of 2 degrees C,” the summary projects. These are tentative figures and the reality could be worse. In any case, the shocks will reverberate across ecosystems.

At 1.5 degrees, marine species are projected to shift their ranges to higher latitudes, leading to habitat loss that would be hard to determine. Coral reefs, already under stress, will decline by 70-90 per cent, and will be wiped out at 2 degrees C.

The 30-million-year-old, 1,400-mile-long Great Barrier Reef off the east coast of Australia, is already altered and degraded in the aftermath of a record-breaking marine heat wave in 2016.

Corals exist in a luminal space, a state of multidimensional belonging.  Corals and algae living in its tissues have a symbiotic relationship that supports both plant and animal life in the ocean.

They cover just one per cent of ocean floor yet they support and sustain 25 per cent of ocean life.

Coral reefs are havens of biodiversity and extremely rich in marine life. They not only help in nitrogen and carbon fixing but also in recycling nutrients and providing a habitat and shelter for many organisms. Thousands of species can found living on a single reef. Coral reefs are thus indispensable to marine food chains.

Coral reefs dissipate wave energy and absorb as much as 97 per cent of it, protecting people from sea level rise and wave action, a 2014 meta-analysis from a team of international scientists, published in Nature Communications, found. About 2.4 billion people live within 60 miles (100 km) of the coast, according to the U.N.

According to the International Coral Reef Initiative (ICRI), India’s 5,790 of coral reefs directly contribute $666 million per year, 0.03 per cent of GDP. Intangibly, they contribute much more. ICRI notes that 61 per cent of India’s coral reefs face high or very high threat levels from human activities.

Warming disintegrates corals in two ways. The first is by bleaching. It prompts corals to expel mutually-beneficent algae, leading them to whiten and eventually die off. Secondly, it turns the ocean more acidic, impairing their ability to build limestone structures.

Ocean acidification will amplify as temperatures rise—even further at 2C—affecting the growth, development, calcification, survival, and thus abundance of a broad range of species, from algae to fish. Shellfish in particular face cataclysmic levels of decline.

The summary says one global fishery model projected a decrease in global annual catch for marine fisheries of about 1.5 million tonnes for 1.5C of global warming compared to a loss of more than 3 million tonnes for 2C of global warming.

At 1.5 degrees yields of key cereal crops will fall but the crisis is expected to be manageable. All bets are off if temperatures rise by 2 degrees.

The 30-million-year-old, 1,400-mile-long, largest living structure on the planet, the Great Barrier Reef off the east coast of Australia, is already altered and degraded in the aftermath of a record-breaking marine heat wave in 2016, according to a study published in Nature

Urban heat islands often amplify the impacts of heat waves in cities.



isks from vector-borne diseases such as malaria and dengue fever are projected to increase with warming from 1.5C to 2C, including potential shifts in their geographic range. Thus, populations that never experienced malaria and other diseases could become vulnerable. The challenge to public health services is easy to visualise if hard to quantify. The additional healthcare costs in a country like the UK, for instance, could go into the billions.

For food security, the summary says “limiting warming to 1.5C, compared with 2C, is projected to result in smaller net reductions in yields of maize, rice, wheat, and potentially other cereal crops, particularly in sub-Saharan Africa, Southeast Asia, and Central and South America; and in the CO2 dependent, nutritional quality of rice and wheat.”

At 1.5 degrees yields of key cereal crops will fall but the crisis is expected to be manageable. All bets are off if temperatures rise by 2 degrees. The decline in nutritional quality is also projected to be greater. With a global population of 7 billion and growing, the portents are ominous.

 Countries in the tropics and southern hemisphere subtropics are projected to experience the largest impacts on economic growth due to climate change should global warming increase beyond 1.5 degrees, the summary states. In other words, the poorest and most vulnerable can expect to be the worst hit.

“Exposure to multiple and compound climate-related risks increases between 1.5C and 2C of global warming, with greater proportions of people both so exposed and susceptible to poverty in Africa and Asia.”

The transition between 2016 and 2030 requires “annual average investment needs in the energy system of around $2.4 trillion.” Inaction will cost much more, the report warns.

The 1.5 degree mark is expected to be hit as early as 2030, barely 11 years away, but certainly in the next 20 years, if emissions don’t drop significantly.

The report suggests measures to limit warming to 1.5 degrees C.



lobal emissions of carbon dioxide need to come down by 45 per cent from 2010 levels (34 billion tonnes) by 2030. The world must reach net zero emissions by 2050, which implies balancing greenhouse gas emissions by removing them from the atmosphere by carbon capture and storage (CCS) technology. Further, 85 per cent of global electricity needs to be renewable by 2050 and coal should be completely phased out.

According to the International Energy Agency, 37 per cent of global electricity generation is from coal, while 27 per cent is renewable, 10 per cent from nuclear, 23 per cent from gas, four per cent from oil in 2017. Total electricity generation was 25,570 TWh (terrawatt hours).

Land use change is also crucial. It requires an allocation of seven million for energy crops. Apart from the changes required at global levels, the report places value on individual actions such as walking or cycling short distances, consuming locally-sourced foods, and so on. The collective savings in energy for transport and processing will be considerable.

The transition requires tons of money. Between 2016 and 2030, it requires “annual average investment needs in the energy system of around $2.4 trillion.” Inaction will cost much more, however, the report warns.

The time for debate, dissembling and waffling is over; this is the time to act, even if the world has to face the consequences of warming that are already locked in.

“This is not a regular IPCC report. This was written to underscore the need for urgent action,” says Jayaraman Srinivasan, Distinguished Scientist at Divecha Centre for Climate Change, and honorary professor, Centre for Atmospheric and Oceanic Sciences, Indian Institute of Science, Bengaluru. He was a lead author of IPCC reports in 1994 and 1995, and lead author of the fourth assessment report (2004-2007).

With India contributing six per cent to global carbon dioxide emissions, “USA, Europe and China need to act to reduce global  CO2 emissions.

“India faces many problems related to water on account of rapid population growth even if there is no warming. If it goes beyond 2C it will make matters worse,” he cautions.

“We need to make radical transformation to reduce import of oil and cut down air pollution.”

India is a vitally important region if we want to understand the implications of global warming both in terms of impact due to its high share in the global population exposed to all kinds of risks, and also by being the fastest growing continent scale economy with the highest poverty in the region, says Joyashree Roy, professor of economics at Jadavapur University. She is a coordinating lead author of chapter 5, “Sustainable Development, Poverty eradication and Reducing Inequalities” in the latest IPCC report and she worked across all chapters. She was one of the network of scientists in the 2007 Nobel Peace Prize awarded to the IPCC.

Scientific assessments with early warnings and a road map for future prospects provide an opportunity for developing countries as they don’t have to lock themselves in carbon-rich infrastructure.

“Compared to other IPCC full assessment reports, working on this special report was challenging because it had very short time limits without compromising the rigour of the assessment and it was a collaboration with all three working groups in one report,” Roy says. 

This report, she continues, tries to focus on investment because that will finally stimulate the economy and help mitigate the worst of the impacts. The major new innovative investments are going to be in energy supply and infrastructure sectors like for transport. So the transformation modelled through the 1.5C pathway envisages a total investment in energy systems of around 2.5 per cent of global GDP between 2016 and 2035.

“Targeted studies in countries like India can provide confidence to national governments/private/multilateral funding agencies to move forward for fund allocation.”

She feels that scientific assessments with early warnings and a road map for future prospects provide an opportunity for developing countries as they don’t have to lock themselves in carbon-rich infrastructure but make sustainable-development-compatible decisions while planning new investments.

“It is a call for how investments in infrastructure with longer life can be prudently decided while managing the emission from existing infrastructure.”

She thinks India is in a better position than many other countries. “There is a national clean energy fund built from a coal cess over multiple years that can be a good source to take care of technology development domestically or with international collaboration towards carbon emission management.

“Both near-term and long-term investment over the years matter. So it is important for India to work out multiple visions for an investment pathway.”



he report forms the backbone of COP24—Conference of Parties where finalising the Paris Agreement work programme is the goal—to be held in December in Poland.

Although it says the impacts are already with us and projects worse things at 2 degrees, the report has a note of hope saying the worst of 2 degrees can be avoided by limiting warming at 1.5, but sounds the alarm over the consequences.

Kevin Trenberth thinks the IPCC doesn’t go quite far enough.

“It’s quite conservative and underplays some things.”

A senior scientist at the US National Center for Atmospheric Research, he was a lead author of the IPCC’s Scientific Assessment Reports in 1995, 2001, and 2007, and was among the network of scientists who shared the 2007 Nobel Peace Prize for the IPCC.

The Global Mean Surface Temp (GMST) has risen about 1.1C since pre-industrial times. Previous reports foresaw enormous damage if GMST shot up to 2 degrees. The present report, though, is focused on what happens at 1.5C warming. The current path shows the world marching right through that target if greenhouse gas emissions continue as they are now.

Trenberth stresses that the report could have addressed the “nonlinearities” in a more robust way. For example, 2016 was the warmest on record for GMST. That was in part due to El Nino prevailing then. He calculates that El Nino would have added 0.2C or so to GMST.

“The increment is small, maybe 0.2C or so: so you can use the El Nino as an example of how small differences in GMST make huge differences: more intense storms, hurricanes, typhoons, monsoon depressions, and flooding, as occurred in recent years in India in various places,” he says.

He also thinks “the real cost of climate change is grossly underestimated  by  economists because they do not deal adequately with the nonlinearities.”

 The report could have provided more thrust on how small changes lead to big effects.  He explains that the best example of nonlinearity is when a threshold is crossed and something breaks.  A common metaphor is “the straw that breaks the camel’s back”.  Increasingly we see examples “where a modest increment in climate change and warming leads to flooding events, or wildfires, or intense storms and strong winds that cause things to break, people and animals to die, and structures to burn.”

Global warming means more heat. It warms land and atmosphere, gets stored in the oceans (causing sea level rise, which is due to the thermal expansion of water and melting ice caps), melts land ice and sea ice, warms water and increases evaporation,  forming atmospheric moisture (water vapour). Warming intensifies the water cycle.

As the non-linearities pile up, warming from the present to 1.5 degrees itself is a catastrophe any way you look at it. 

Although it can get extremely hot in the pre-monsoon due to warming, “it is much more the changes in precipitation to more extremes: longer dry spells, heat waves and wildfires on one hand, and then more intense rains, more severe storms and risk of flooding on the other hand. All of these can occur without much increase in GMST: the heat goes into the more intense weather systems,” Trenberth says.

In short, even without the 1.5 degree rise, we have increasing warming impacts.

The report, he says, missed their latest work detailing  heat loss from  the ocean caused by the storm (evaporation) in the case of Harvey, which they found equalled the heat generated by rainfall. 

This suggests that had the ocean been cooler, there would not have been so much rain, and the storm would not have been as intense. 

Moreover, he says, “the risk has been known for some time, at least since the active year of 2005 when Katrina devastated the New Orleans area.  Why hasn’t there been more preparation for the sort of thing that was clearly expected sooner or later?  Why isn’t there better recognition that the warnings were already out there, and global warming consequences are already with us?

As the non-linearities pile up, warming from the present to 1.5 degrees itself—not to speak of the warming from 1.5C to 2C—is a catastrophe any way you look at it. And it gets worse by the day. The only saving grace is the planet will continue to be even if we are not there to see it.