Intergovernmental Panel on Climate Change report affirms need for Net Zero
The much anticipated global climate science report Climate Change 2021: The Physical Science by Working Group I of the UN’s Intergovernmental Panel on Climate Change (IPCC) has been released. The report brings together the latest advances in climate science, combining multiple lines of evidence from paleoclimate, observations, process understanding, and global and regional climate simulations.
As the first of four contributions to the IPCC’s Sixth Assessment Report (AR6), the report synthesizes understanding of the current state of the climate, including how it is changing and the role of human influence, and the state of knowledge about possible climate futures, climate information relevant to regions and sectors, and limiting human-induced climate change.
With this up-to-date physical understanding of the climate system and climate change, the report finds that increasing global warming is leading to increased frequency and intensity of hot extremes, marine heatwaves and heavy precipitation, agricultural and ecological droughts in some regions, and proportion of intense tropical cyclones, as well as reductions in Arctic sea ice, snow cover and permafrost. The findings result in five key takeaways:
- 1.5°C warming will be surpassed by 2040. This is around ten years earlier than previous estimates due to the incorporation of new datasets in the estimate of historic temperature rise, including from the fast-warming Arctic.
- Extreme temperatures and weather events are human-induced. Extensive developments in attribution science since the previous IPCC report have resulted in “high confidence” that human activities are the main driver of these extremes.
- Regional climate impacts are discernible. Temperature and hydrological extremes at a regional level are able to be analysed and projected, with results available in an interactive atlas. Northern Hemisphere high latitudes are particularly susceptible to warming, and are projected to warm by two to four times the level of global warming.
- Irreversible tipping points are a real possibility. Abrupt responses and tipping points of the climate system cannot be ruled out as higher global warming levels increase the probability of low-likelihood, high impact outcomes. Such tipping points include Gulf Stream shut-down, Antarctic ice sheet melt and forest dieback (such as in a recent study finding that degraded areas of the Amazon now emit more carbon than they absorb).
- Methane levels have exceeded safe limits. Methane levels are higher than at any point in the past 800,000 years and are likely to be raised further by ecosystem responses to global warming such as thawing permafrost and wildfires. This is of concern due to methane’s global warming impact being 84 times higher than CO₂ over a 20-year period.
The report highlights that “limiting human-induced global warming to a specific level requires limiting cumulative CO₂ emissions, reaching at least net zero CO₂ emissions, along with strong reductions in other greenhouse gas emissions.”
Professor Nathalie Seddon, NbSI director, states: “What is very clear is the urgent need to slash emissions. If we do not, then continued warming will undermine the capacity of ecosystems to sequester and store carbon, leading to their conversion to net sources rather than net sinks of greenhouse gases. It is also vital that pathways to achieving net zero, whether through technological or nature-based approaches, do not compromise nature recovery and support biodiversity conservation and other societal challenges.”
NbSI Senior Associate Alison Smith notes: “The stark warnings of this report emphasise that we need to accelerate decarbonization at rates never achieved before, almost eliminating fossil fuel use, and cutting our over-consumption of energy and materials to sustainable levels. It is also essential to protect the vast amounts of carbon stored in ecosystems such as native forests, fens, peatlands, ancient grasslands and marine sediments.”
“Even if we accelerate decarbonization at rates never achieved before, only reducing emissions is not sufficient to achieve net zero. It is also necessary to actively remove and store carbon dioxide from the atmosphere through Negative Emissions Technologies (NETs). This includes removing carbon from the atmosphere via carefully designed, ecologically sound and socially equitable nature-based solutions that restore degraded ecosystems and ensure the sustainable management of working lands. However, other NET options such as Bioenergy with Carbon Capture and Storage (BECCS) should be used with caution: they use vast areas of land, and do not provide the multiple long-term benefits of nature-based solutions, often compromising food security and biodiversity,” adds Dr Cécile Girardin, NbSI Technical Director.
Transformative change is needed to reduce and remove emissions (mitigation), and address their impacts (adaptation). Such action should not rely solely on technological innovations, but also innovation in nature-based solutions and governance that will play key roles in reducing, mitigating and adapting to climate change.
Download the full Climate Change 2021: The Physical Science report, or find a range of digested versions such as the Summary for Policymakers on the IPCC report webpage.