Guest blog: Time for a reality check: the Paris Agreement won’t prevent dangerous climate change—we need a Plan B
Guest blog by Graeme Taylor and Sue Vink
Why the Paris climate targets will be missed
While no one likes to cast doubt on the 2015 Paris Agreement—it’s
like saying that the Emperor has no clothes—the grim reality is that its
targets will not be met. Moreover, even if the world achieves zero net
emissions, existing greenhouse gases will push global temperatures past safe
levels.
Despite the international treaty, greenhouse gas emissions
(GHG) have risen every year. On the current trajectory, by 2100 average global temperatures
are likely to increase above preindustrial levels by a catastrophic 3°C - 4°C. Even
if the latest national pledges are fully implemented, temperatures will increase
by a devastating 2.4°C (Climate Action Tracker 2021).
To achieve the Paris goals three extremely ambitious targets
must be met (Rockström et al. 2017):
- Global CO2 emissions should decline by 50% per decade.
- Net emissions from agriculture and deforestation must be cut to zero by 2050 (at the same time as more food is required to meet the needs of a growing global population).
- Carbon dioxide removal technologies will have to be rapidly developed and scaled up to remove 5 gigatons of CO2 per year from the atmosphere by 2050.
Significant progress is being made. Renewable energies are
now the cheapest options in much of the world. However, only 6 out of 46 clean
energy technologies and sectors are currently on track to help hit emissions
reduction targets (IEA 2020); and although many mitigation plans rely on the
widespread deployment of carbon capture and storage, in 2018 there was still a
1 to 300 disparity between actual and necessary investment (WEF 2018).
Technological breakthroughs will accelerate the transition
to zero net emissions. Nevertheless, the 2°C limit will still be overshot due
to systemic inertia from existing greenhouse gases, warming oceans, and the
decades required to replace existing infrastructure (e.g., Zhou, Zelinka,
Dessler and Wang 2021). Carbon dioxide levels are already 416 ppm: to bring the
Earth back into an energy balance and prevent further warming, the amount of CO2
in the atmosphere needs to be reduced to 353 ppm (Von Schuckmann et al. 2020).
All CMIP6 models suggest that the Agreement’s 1.5°C target
will be breached around 2030 or 2035. Further, although all scenarios assume
that temperatures can be returned to safe levels by 2100 through large-scale
carbon dioxide removal (CDR), no plans have been made to develop and deploy the
required CDR geoengineering technologies.
In reality the world is still many decades away from ending
net greenhouse gas emissions, let alone deploying viable carbon removal
technologies. These problems lead to the following logical conclusions: (a)
dangerous climate target overshoot is almost inevitable; and (b) solar
radiation management (SRM) geoengineering will be required to constrain
temperature overshoot until greenhouse gas concentrations are stabilized at
safe levels (Figure 1). However, not only are SRM technologies not ready for
large-scale deployment, but they cannot be used until their risks are
understood and mitigated.
Figure 1. Possible global temperature trajectories with or without geoengineering. |
Because the Paris Agreement (the only existing international treaty to restrict greenhouse gases) is unlikely to prevent dangerous climate change, humanity must now urgently develop and reach agreement on a feasible back-up strategy—a realistic “Plan B”.
Both CDR and SRM geoengineering will be needed to restore a
safe, stable climate
Mitigation efforts need to focus on accelerating the global
transition to a net-zero carbon emissions economy. However, climate
geoengineering will also have to be deployed to prevent temperatures exceeding
safe limits during the long period that it will take to transition to a clean economy,
remove carbon dioxide from the atmosphere, and re-establish a safe and stable
climate.
The question of whether or not humanity should engage in
geoengineering is moot. The increases in global temperatures since the
Industrial Revolution demonstrate humanity’s ability to geoengineer the earth’s
atmosphere through the release of massive quantities of greenhouse gases.
Earth’s climate must now be re-engineered toward stable conditions similar to
the last 10,000 years of the Holocene, during which natural and human systems
assumed their current form.
However, to remove sufficient CO2 from the
atmosphere to meet the Paris targets it will be necessary to create a new
carbon sink on the scale of the ocean sink. The potential capacity of many CDR
measures is also constrained by available land, water, nutrients, environmental
concerns and/or cost. Additionally, since CO2 would only be removed
slowly, CDR methods will not have an appreciable effect on the global climate
for decades.
SRM methods also have risks and drawbacks. While injecting
sulphate aerosols into the stratosphere may be a rapid, effective and
relatively inexpensive way to cool global temperatures, it may negatively
impact photosynthesis and precipitation. Other mineral aerosols may overcome
some of these problems (e.g., Oeste, de Richter, Ming, and Caillol 2017). A
moderate amount of solar reduction may shave peak temperatures and produce
temperature and precipitation values in all regions that are closer to the
preindustrial climate (Tilmes et al. 2020).
Another risk is that the promise of cheap, quick
geoengineering fixes to global warming will reduce political pressure for
decarbonisation. This is a serious issue as SRM will not prevent rising levels
of atmospheric CO2 from acidifying the oceans with catastrophic
impacts on marine life.
Because there are still many unresolved questions about
climate geoengineering, research is urgently needed on the relative
feasibility, risks and costs of all potential mitigation measures. The critical
problem that must be addressed is that although CDR methods are safer than SRM,
they will act too slowly to prevent dangerous overshoot.
The key elements of a realistic climate strategy
While it could be dangerous to deploy untested methods that
are either ineffective or do more damage than good, the consequences could be
catastrophic if geoengineering was not deployed in time to prevent overshooting
safe temperatures.
Opponents of climate geoengineering need to recognise that
the alternative to researching and deploying geoengineering is to leave all
efforts to limit temperature increases to reducing emissions, a strategy that
would be almost certain to fail (Aldy and Zeckhauser 2020).
Consequently, research is urgently needed on the comparative risks of overshooting safe temperatures versus the risks of various mitigation approaches. This research should lead either to the development of a much stronger, viable Paris Agreement [i.e., “Plan A”, version 2], or an alternative, internationally agreed on “Plan B” (Figure 2).
Figure 2. A proposal for developing a viable climate overshoot risk management plan. |
Not moving off the current trajectory will result in a world that is unstable and dangerous for life as we know it. The following steps must be taken to prevent dangerous temperatures:
1. Because mitigation efforts under the existing Paris
Agreement are unlikely to prevent dangerous climate change, priority must be
given to developing an alternative strategy—a much stronger Paris Agreement
and/or a “Plan B”.
2. Climate change is a risk management problem. It requires
a comparative assessment of the likely risks and costs of acting or not acting
to prevent undesirable impacts.
3. Overshoot risks have been seriously underestimated.
Research is urgently required on climate inertia, lags, feedbacks, tipping
points and timelines.
4. Even if met, the Paris Agreement targets will not result
in a safe, stable climate since climate stabilization requires reducing the
Earth energy imbalance to approximately zero.
5. Greater insights are needed on the necessity,
feasibility, risks, costs and timelines of the full range of mitigation
options.
6. Because climate overshoot cannot be prevented without
large-scale geoengineering, knowledge gaps need to be urgently filled on all
potential geoengineering methods. A critical issue is that although CDR methods
are safer than SRM, they will act too slowly to prevent dangerous overshoot.
7. A realistic plan will need to combine three approaches:
(a) rapidly reducing GHG emissions; (b) deploying CDR geoengineering to draw
down atmospheric carbon; and (c) using solar geoengineering to keep
temperatures within safe limits until CO2e levels have been adequately
reduced.
8. A two-track approach utilising “coalitions of the willing” will allow the simultaneous application of both a strengthened Paris Agreement and a realistic “Plan B”.
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