Overshooting 1.5°C warming would lead to irreversible impacts: IPCC report

Overshooting 1.5°C warming will lead to irreversible impacts and risks for human and natural systems, all growing with the magnitude and duration of overshoot, an Intergovernmental Panel on Climate Change (IPCC), the key scientific authority on climate crisis, warned on Monday.

Making it clear that the 1.5°C goal will be breached within next few years even in the lowest emissions scenario, IPCC’s synthesis report said rise in average global temperature could be gradually reduced again by achieving and sustaining net negative global CO2 emissions.

In its final report of the panel’s sixth assessment cycle until at least 2028 (seventh assessment cycle), IPCC indicated preventing overshoot of 1.5°C was pretty much a matter of survival now as every increment of global warming will intensify multiple and concurrent hazards and result in irreversible adverse impacts on polar, mountain, and coastal ecosystems, impacted by ice-sheet, glacier melt, or by accelerating and higher committed sea level rise.

Also Read: Allowing 1.5°C warming will mean more extreme weather: Jean-Pascal van Ypersele

In a direct blow to the fossil fuels industry, IPCC said CO2 emissions from existing fossil fuel infrastructure without abatement would exceed the remaining carbon budget for 1.5°C and deplete the carbon budget for 2°C too.

The only way to prevent overshoot is to ensure rapid, deep and, immediate greenhouse gas emissions reductions in all sectors in this decade.

“Keeping warming to 1.5°C above pre-industrial levels requires deep, rapid and sustained greenhouse gas emissions reductions in all sectors. Emissions should be decreasing by now and will need to be cut by almost half by 2030, if warming is to be limited to 1.5°C,” IPCC said in a statement.

“Today’s IPCC report is a how-to guide to defuse the climate time-bomb. It is a survival guide for humanity. As it shows, the 1.5-degree limit is achievable. But it will take a quantum leap in climate action. This report is a clarion call to massively fast-track climate efforts by every country and every sector and on every timeframe. In short, our world needs climate action on all fronts -- everything, everywhere, all at once,” said UN Secretary general, Antonio Guterres during the launch of the report.

He also called for fast-tracking of net zero goals in line with what IPCC has recommended.

“I have proposed to the G20, a Climate Solidarity Pact – in which all big emitters make extra efforts to cut emissions, and wealthier countries mobilize financial and technical resources to support emerging economies in a common effort to keep 1.5 degrees alive… It starts with parties immediately hitting the fast-forward button on their net zero deadlines to get to global net zero by 2050 – in line with the principle of common but differentiated responsibilities and respective capabilities, in light of different national circumstances. Specifically, leaders of developed countries must commit to reaching net zero as close as possible to 2040, the limit they should all aim to respect,” he added.

As far as future warming is concerned, IPCC says with higher certainty compared to previous AR 5 (2013-14) that we can expect global warming in the range of 1.4°C for a very low GHG emissions scenario to 2.7°C for an intermediate GHG emissions scenario and 4.4°C for a very high GHG emissions scenario.

Widespread and rapid changes in the atmosphere, ocean, cryosphere and biosphere have already occurred due to global warming of 1.1°C, IPCC said.

“Human-caused climate change is already affecting many weather and climate extremes in every region across the globe. This has led to widespread adverse impacts and related losses and damages to nature and people. Vulnerable communities who have historically contributed the least to current climate change are disproportionately affected,” it said.

These findings have strengthened since the AR 5 cycle of IPCC.

Human influence has likely increased the chance of compound extreme events since the 1950s, including increases in the frequency of concurrent heatwaves and droughts.

Approximately 3.3–3.6 billion people are highly vulnerable to climate change.

Between 2010 and 2020, human mortality from floods, droughts and storms was 15 times higher in highly vulnerable regions, compared to regions with very low vulnerability.

Climate change has caused widespread adverse impacts and related “losses and damages” to nature and people that are unequally distributed across regions.

“Climate justice is crucial because those who have contributed least to climate change are being disproportionately affected,” said Aditi Mukherji in a statement, one of the 93 authors of this Synthesis Report, the closing chapter of the Panel’s sixth assessment.

The IPCC also flagged that adaptation limits have been reached by several communities which means they will no longer be able to cope with extremes of climate change.

Soft limits to adaptation are currently being experienced by small-scale farmers and households along some low-lying coastal areas. Some tropical, coastal, polar and mountain ecosystems have reached hard adaptation limits.

Nationally determined contributions submitted by countries till COP 26 in Glasgow (by October 21) may make preventing even 2°C warming unlikely, IPCC said in its report.

Global GHG emissions in 2030 implied by nationally determined contributions (NDCs) announced by October 2021 make it likely that warming will exceed 1.5°C during the 21st century and make it harder to limit warming below 2°C.

There are gaps between projected emissions from implemented policies and those from NDCs and finance flows fall short of the levels needed to meet climate goals, it said.

With every additional increment of global warming, changes in extremes continue to become larger.

Continued global warming is projected to further intensify the global water cycle, including its variability, global monsoon precipitation, and very wet and very dry weather and even change seasons, the IPCC said adding that compound heatwaves and droughts are projected to become more frequent, including concurrent events across multiple locations.

Due to relative sea level rise, current 1-in-100-year extreme sea level events are projected to occur at least annually in more than half of all tide gauge locations in all emission scenarios.

There will be intensification of tropical cyclones and/or extratropical storms, and increases in aridity and fire weather.

Further, the IPCC flagged that climatic and non-climatic risks will increasingly interact, creating compound and cascading risks that are more complex and difficult to manage.

“The new IPCC report shows the writing clearly on the wall. Governments have no excuse to ignore the emphatic warning for this critical decade. They must act fast to reject fossil fuels and stop any new expansion of oil, gas and coal. The blueprint for climate action presented by the IPCC is not short of solutions and infused with enough hope… Every fraction of a degree of warming puts us closer to breaching the 1.5°C survival threshold. The governments must strengthen efforts to protect communities from worsening and irreversible climate impacts, such as sea-level rise and melting of glaciers, which pose an existential threat to many communities. Scaling up finance must be the key lever to make the transition to a climate stable future in a just and equitable manner,” said Harjeet Singh, Head of Global Political Strategy, Climate Action Network International who was an observer at the IPCC approval meeting in Interlaken, Switzerland ahead of the report release.

Equity and climate justice

For the first time, IPCC has a box on global modelled emission pathways which may be biased and inequitable. Those based on cost effective approaches contain regionally differentiated assumptions and outcomes, and have to be assessed with the careful recognition of these assumptions. Most do not make explicit assumptions about global equity, environmental justice or intra-regional income distribution, the IPCC said.

“IPCC is neutral with regard to the assumptions underlying the scenarios in the literature assessed in this report, which do not cover all possible futures,” the report said.

Experts in the past have highlighted the issues with IPCC’s modelled pathways.

A policy brief released by prepared by the Climate Change Programme at the MS Swaminathan Research Foundation (MSSRF), Chennai, and the Energy, Environment and Climate Change Programme at the National Institute of Advanced Studies (NIAS), Bengaluru in November last year said that the scenarios for global mitigation pathways considered by IPCC project a highly unequal future world that perpetuates most inequalities, HT had reported.

“The economic pathways and models used especially the mitigation models are not real world and don’t present all possible futures. They are built by economists who follow a certain school of economics and they are structurally biased. Several analyses have highlighted this bias, including the fact that most scenarios assume the rich parts of the world to get richer and poor parts poorer and delay climate action into the future,” Lili Fuhr from the Center for International Environmental Law had said on Friday.

The IPCC approval meeting in Interlaken where 195 countries negotiated and approved the summary for policy makers was delayed by nearly 20 hours mainly because of contentions over equity related matters among developed and developing countries.

“There were a number of really legitimate concerns, and delegations wanted to bring them to the table. That just took time to go through. Those included, discussing the scenarios and pathways, equity across the board, carbon budgets, climate finance, a number of issues, because each and every country has a different focus. Small countries and developing countries came with small delegations. Some didn’t come at all, some with only one person so to organise a process that was both effective and speedy and also inclusive was quite a challenge, and didn’t work out in the best way throughout the entire week,” Fuhr added.

Carbon capture

The IPCC said carbon dioxide removal (CDR) will be necessary to achieve net-negative CO2 emissions. Net zero GHG emissions, if sustained, are projected to result in a gradual decline in global surface temperatures after an earlier peak. This was one of the contentious issues discussed at the meeting in Interlaken.

Only a small number of the most ambitious global modelled pathways limit global warming to 1.5°C by 2100 without exceeding this level temporarily.

Achieving and sustaining net negative global CO2 emissions, with annual rates of carbon dioxide removal greater than residual CO2 emissions, would gradually reduce the warming level again, the IPCC said while also flagging that CDR technologies are high risk and have several feasibility concerns.

“The larger the overshoot, the more net negative CO2 emissions would be needed to return to 1.5°C. Transitioning towards net zero CO2 emissions faster and reducing non-CO2 emissions such as methane more rapidly would limit peak warming levels and reduce the requirement for net negative CO2 emissions, thereby reducing feasibility and sustainability concerns, and social and environmental risks associated with CDR deployment at large scales,” the report said.

IPCC mentions biological CDR methods like reforestation, improved forest management, soil carbon sequestration, peatland restoration and coastal blue carbon management can enhance biodiversity and ecosystem functions, employment and local livelihoods.

“However, afforestation or production of biomass crops can have adverse socio-economic and environmental impacts, including on biodiversity, food and water security, local livelihoods and the rights of Indigenous peoples, especially if implemented at large scales and where land tenure is insecure,” IPCC said.