Climate Brief: Using IPCC to quantify greenhouse gas emission reductions

Introduction: Goals of COP26 in context

Current Five-Year Emission Cutting Plans Are Not Enough

The Paris agreement reached in 2015 committed countries to limiting global heating to “well below” the 2^oC over pre-industrial levels, while striving for a 1.5^oC cap through extensive reduction in greenhouse gas emissions. As part of the Paris accord, countries were to submit new or updated climate plans (Nationally Determined Contributions (NDCs)) every five years. 143 of 197 countries had done so in time to assess their impact on global warming before COP26. Note that two of the biggest greenhouse gas emitters, China and India, did not submit updated NDCs.

In advance of COP26, the NDCs, including China and India’s from 2015, were assessed for both global carbon emissions and with climate models to see the resulting impact on global warming. The results were sobering: the combined NDCs of all countries is not sufficient to meet the Paris agreement’s 1.5^oC goal. The following graphic shows the warming projections based on various scenarios.

Current pledges result in an global mean temperature 2.4^oC higher by 2100. At current policies, this increase would be 2.9^oC. Meeting current net zero targets keeps heating to 2.0^oC which, given what is already becoming commonplace at a warming of 1.1^oC in 2021, is likely not sufficient to reduce the hardship, suffering, and potential mass migrations of peoples seeking a more livable climate even now.

What is necessary to limit warming to 1.5^oC

The 143 country pledges, while reducing greenhouse gas emissions by 83-88% by 2050, excludes China and India, which if included results in a decrease of only about 55% by 2100 (solid blue line above). The aggregated pledges limiting warming to only 1.5^oC require a 50% reduction of emissions by the end of this decade.

So, what did Day Four accomplish in terms of meeting this very ambitious goal? I’m going to limit this report to what I considered the two main events that directly address this question:

• 10 New Insights in Climate Science, 2021 Report, which summarizes the new knowledge acquired on the climate system, including social aspects, and
• Accelerated Just and Inclusive Energy Transition, which discusses coming to an agreement of what a just and inclusive transition looks like

IPCC 6th Assessment as Incentive

At a news conference held early on Day 4, a news conference was held to discuss new scientific knowledge and key insights in climate science for 2021. This provided a good summary of the important talking points for attendees involved in negotiations on emission levels acceptable for COP26, or for anyone wanting to discuss what we know about global warming and what’s necessary to limit it to as low as possible.

new scientific knowledge

One of the major climate science advances, though not necessarily providing good news, was a better idea of the sensitivity of climate to greenhouse gases. This has resulted in a narrowing of the expected warming for global mean temperatures. “Middle-of-the road” warming is now more likely, higher and lower values less likely. This also allows COP26 (and beyond) to have a better handle on what emissions target is necessary to minimize high impact weather and climate events.

The world can now have increased confidence in the analysis of risks of crossing tipping points, such as the breakdown of the Atlantic Meridional Overturning Circulation (AMOC), loss of Arctic Sea Ice, and risk of significant melting of the Greenland ice sheet, among others. We also now can discern important potential coupling and feedbacks among pieces of the climate system. A good example was shared showing relationships between different elements of the Atlantic and land areas around it, which I screen captured and have displayed to the right.

In the graphic, we see the Greenland and West Antarctic Ice Sheets will start “disintegrating” at a temperature rise of between 1-3^oC. We’re already seeing this clearly for Greenland, and see hints of ice loss in the West Antarctic. The influx of fresh water from the melting ice sheets into the areas of deep water formation will reduce the salinity and reduce deep water formation southeast of Greenland and north of the west Antarctic. This will in turn reduce AMOC northward transport of warm, salty near-surface water once a warming threshold of 3-5^oC has been reached. Reduction of warm water transport by the Gulf Stream and North Atlantic Drift Current will result in eastern American and western European cooling, especially in winter; changes in precipitation in the Gulf region of North America could be positive or negative. Weakening of the AMOC will also result in the accumulation of excess heat in the South Atlantic, and drying and dieback of the Amazon rainforest. Finally, melting ice will increase sea level everywhere over the globe, a destabilizing impact particularly for low-lying nations.

ten key insights in climate science 2021 report

Keeping in mind The list of insights in the climate science report were as follows:

1. Our current understanding of the climate system tells us that a 1.5^oC limit to the mean global temperature (MGT) increase is still achievable, but requires far more reduction in emissions than has been promised to date:
   1. To have a 50% chance of limiting MGT increase to 1.5^oC, greenhouse gas emissions must decrease by 2 gigatons (5%) per year starting now
   2. To have a 2/3 chance, the decrease must be double that (10% or 4 Gt per year)
2. There can be no “safe landing” (<=1.5^oC) without similar decreases in methane (CH₄) and nitrous oxide (NO₂).
3. There has been a substantial increase in “megafires”, which result in positive feedbacks to global warming (reduced albedo, increased CO₂ emissions).
4. Tipping points are real (see example above). We now have a “moderate” risk of high impact events at a MGT increase of about 1.5^oC, rather than the 4^oC increase thought back in 2001.
5. Climate action must be just!
   1. (ed.This statistic blew me away, though I shouldn’t be surprised.)  To have equity in climate action, the richest 1% of countries would need to reduce emissions by a factor of 30 (97%). The poorest 50% would be able to increase their emissions by a factor of 3 (300%) with no negative impact.
6. Household lifestyle/behavioral changes are a crucial, but often overlooked, opportunity for climate action (i.e. live a 1.5^oC lifestyle!).
7. Political challenges impede the impact of effective carbon pricing. Only 22% of emissions come from countries with carbon pricing, and the pricing is too low.
8. Nature-based solutions are important, but must be robust. Caution must be taken in pricing carbon offsets, to not double count carbon sinks already accounted for in our climate models.
9. The ocean is the “resilient” thermostat of the climate system. However, the ocean is under threat from multiple sources: habitat destruction, climate change, pollution, invasive species, and direct exploitation (e.g. overfishing). Building resilient marine ecosystems is achievable through climate-adapted conservation by, for example, expanding marine conservation areas from 7.8% to 30% (I presume by mid-century).
10. The cost of climate change mitigation is justified by the benefits to the health of humans and of nature. Such benefits need to be considered as offsetting mitigation costs.

Ms Patricia Espinosa, Executive Secretary of the UN Framework Convention on Climate Change (UNFCCC) ended the presentation with a short talk. She is concerned that we cannot constrain global mean temperature increase to 1.5^oC, but is also hopeful since it’s still possible to achieve this vital goal if we take decisive action during the current decade. She sees COP26 as “… yet another appeal to our rationality and sanity as a species … The evidence of the climate crisis is conclusive, that we must choose scientific knowledge over self-serving and ultimately deluded views that place private interests over collective well-being.”

The Rest of Day 4: Energy

On Day Four of COP26, the theme was Energy, with the Headline Event titled “Accelerating a Just and Inclusive Energy Transition”. Boatsie has done a great job covering the energy and finance issues revealed in the energy talks, so I’ll refer you to her COP26 diary. Pay particular attention to the areas discussing the likelihood (and barriers) to converting to a renewable energy economy soon enough to save us from ourselves.

A reminder: everyone can listen to each day’s proceedings by going to the UNFCC list of on demand and active session videos.

The writers in Climate Brief work to keep the Daily Kos community informed and engaged with breaking news about the climate crisis around the world while providing inspiring stories of environmental heroes, opportunities for direct engagement, and perspectives on the intersection of climate activism with spirituality, politics, and the arts.