[ The Case for Climate Cooling Research ]

The case for climate cooling research.

Why many scientists believe climate cooling research has become an essential complement to emissions reductions, adaptation and carbon dioxide removal.

The four pillars References
CLIMATE SYSTEM↓CO₂Mitigation🛡AdaptationC↓Carbon Removal☀↑Cooling
A guided walkthrough
[ [ 01 · Why this matters now ] ]

A rapidly warming world

Global emissions continue to rise, atmospheric CO₂ continues to climb, and warming is accelerating faster than most projections a decade ago anticipated. This modern physical context is the reason many researchers now believe additional lines of inquiry — including climate cooling — deserve serious, careful attention.

Global CO₂ emissions
Record high

2024 fossil CO₂ ~37.4 Gt — a new record

Source
Atmospheric CO₂
~422 ppm

NOAA Mauna Loa, still rising ~2.5 ppm / yr

Source
Warming trajectory
~2.7 °C by 2100

UNEP Emissions Gap 2024, current policies

Source

Under the Paris Agreement, limiting warming to 1.5 °C would require approximately halving global emissions by 2030. The UNEP Emissions Gap Report 2024 concludes that current policies place the world on track for roughly 2.6 – 3.1 °C of warming this century. Adaptation alone cannot eliminate climate risk at that level of warming, and carbon dioxide removal — while essential — will take decades to scale to climatically relevant magnitudes.

As James Hansen and colleagues put it in Global Warming in the Pipeline, the observed acceleration in Earth’s energy imbalance is reshaping the questions researchers now feel obliged to ask (Hansen et al., 2023). In this context, climate cooling research is increasingly viewed as an important area of investigation — not a replacement for mitigation, adaptation or CDR, but an additional line of inquiry within an integrated response.

[ [ 02 · Warming already committed ] ]

A substantial amount of warming is already locked in

Because the climate system responds slowly, additional warming is now built into the system — even if emissions were to fall rapidly from tomorrow. This physical reality is a central reason why many scientists now consider climate cooling research an important complement to mitigation, adaptation and carbon dioxide removal.

Four physical realities together define what climate scientists call ‘committed warming’:

  • Ocean heat uptake. The ocean has absorbed more than 90% of the excess heat from greenhouse forcing (IPCC AR6, 2021), buffering surface warming — but that stored heat continues to work its way back into the atmosphere.
  • Delayed climate response. Full equilibrium warming from today’s CO₂ concentration is estimated at considerably more than the ~1.2 – 1.3 °C already observed (Hansen et al., 2023).
  • Long atmospheric lifetime of CO₂. A significant fraction of emitted CO₂ remains in the atmosphere for centuries to millennia (Joos et al., 2013).
  • A persistent, growing radiative imbalance. CERES satellite observations show Earth’s energy imbalance has approximately doubled since the mid-2000s (Loeb et al., 2021).
Why this matters for the case for research

If additional warming is already committed, then understanding the potential benefits, limitations and risks of climate cooling — through rigorous, transparent scientific research — is a responsible course of action. Refusing even to study these options does not remove the underlying risk. It simply removes a set of informed choices from those who will have to live with the consequences.

“Global warming in the pipeline is greater than prior estimates. Eventual global warming due to today's greenhouse gas forcing alone would reach about 10 °C… unless human-made aerosols continue to mask a large fraction of the greenhouse forcing.”
— Hansen et al., Global Warming in the Pipeline (2023)
“Every increment of warming avoided matters. Every choice matters. Every year matters.”
— IPCC AR6 Synthesis Report (2023)
[ [ 03 · An important distinction ] ]

Research is not deployment

One of the most common sources of confusion in this conversation is treating the study of cooling technologies as if it were the same thing as the decision to deploy them. It is not. Research exists to improve understanding, identify risks and limitations, reject unsuitable approaches, strengthen governance and support better future decisions — not to commit anyone to action.

What research does
  • Improves scientific understanding of physical processes
  • Quantifies potential benefits, risks and side-effects
  • Identifies unintended consequences before they occur
  • Informs governance frameworks and international norms
  • Helps distinguish credible options from speculative ones
  • Preserves the freedom of future societies to choose wisely
What research does not do
  • Commit any nation, community or actor to deployment
  • Replace or slow the essential work of decarbonisation
  • Guarantee that any given technology will prove viable
  • Remove the need for democratic oversight and consent
  • Substitute for open, inclusive public conversation

This distinction is drawn explicitly in the U.S. National Academies (2021) report and in the Oxford Principles on Geoengineering Governance, both of which frame research as a prerequisite for — not a replacement for — informed democratic choice. Understanding a possibility is not the same as pursuing it; refusing to understand it is itself a choice, with its own consequences.

[ [ 04 · An integrated climate response ] ]

Four complementary pillars

Effective climate action requires four complementary pillars. Rapid emissions reductions remain the long-term foundation. Adaptation protects people and ecosystems from warming already underway. Carbon dioxide removal addresses historical emissions. Climate cooling helps reduce dangerous surface heat as the transition continues. None replaces another; each addresses a different aspect of climate risk; and climate cooling is an additional tool that complements — never replaces — the others.

Fig. 9 · A stable climate — four pillars, one dome
Dome unsupported
A STABLE CLIMATEEMISSIONSADAPTATIONCO₂ REMOVALCOOLING

Climate stability depends on multiple complementary strategies working together. No single approach is sufficient, and none is a substitute for another. Removing one weakens the resilience of the whole system.

Pillar 1
Emissions

Rapid emissions reductions

The long-term foundation. Every other pillar buys time or manages risk while decarbonisation proceeds.

Pillar 2
Adaptation

Adaptation

Protecting people, ecosystems and infrastructure from warming already locked in.

Pillar 3
CO₂ removal

Carbon dioxide removal

Drawing down historical emissions over decades to centuries to lower the long-run temperature ceiling.

Pillar 4
Cooling

Climate cooling

Restoring reflectivity and enhancing radiative loss — with surface cooling as the safest, most governable form.

This four-pillar framing is broadly consistent with the IPCC AR6 Working Group III (2022) mitigation assessment, which treats mitigation, adaptation and carbon removal as complementary — and increasingly considers solar radiation modification within its risk-management framing.

[ [ 05 · Where MEER fits ] ]

MEER's approach: surface-based, local, reversible

MEER's work centers on surface-based cooling — reflective roofs, canopies, coatings, materials and land-surface interventions. This is a fundamentally different class of intervention from many of the atmospheric proposals traditionally associated with geoengineering, and its characteristics change most of the classical assumptions about who governs, what is reversible, and where the benefits fall.

Passive surface cooling

No injection into the atmosphere. Cooling occurs through reflection and enhanced thermal emission at the Earth's surface.

Local & regional governance

Cities, communities and landowners decide what to install on their own surfaces — no global coordination is required.

No termination shock

Unlike stratospheric interventions, removing a reflective roof or canopy does not cause a rapid warming rebound.

Measurable in the field

Effects can be directly measured with instruments on and around installations — not inferred from global models alone.

Modular & reversible

Installations are additive, incremental, and can be added, modified or removed as evidence and needs evolve.

Immediate co-benefits

Reduced indoor heat, lower cooling energy demand and improved human thermal safety — value delivered before global effects.

Why the distinction matters
Surface cooling is not a lever pulled once at planetary scale. It is additive infrastructure — installed where it is needed, governed by the communities and institutions it affects, measurable directly in situ, and reversible without cascading global consequences. In every respect that made the original moral hazard concern sharp, surface cooling looks materially different: it is incremental, local, transparent, and delivers immediate protective benefits to people living through heat today, while contributing to the wider effort to restore Earth’s reflectivity over time.
From Science to Scale How surface cooling works
[ [ 06 · A brief history ] ]

How the moral hazard discussion has evolved

Moral hazard is an economic concept that long predates geoengineering. It has been raised in relation to carbon pricing, offsets, afforestation, soil carbon, CCS, direct air capture and other forms of carbon dioxide removal — and, after 2006, in relation to solar radiation management. Understanding its broader history helps place the SRM debate in proper context before returning to the science.

01Economic concept

A long-standing idea from insurance economics

Moral hazard is not a new concept, and it did not originate with geoengineering. It comes from insurance economics, where it describes how behavior can change once a risk is insured against, and it has been applied across many policy contexts for decades (Hale, 2012).

02Applied to climate policy

A recurring concern across many climate solutions

The concern surfaces whenever a proposed climate response goes beyond reducing emissions at source. Critics have raised it in relation to carbon pricing, carbon offsets and credits, afforestation and reforestation, soil carbon and regenerative agriculture, carbon capture and storage (CCS), direct air capture (DAC), enhanced weathering and BECCS — the worry in each case being that a plausible future fix could weaken near-term incentives to cut emissions.

03Applied to SRM

Rising prominence after 2006

Following the revival of modern SRM research after Paul Crutzen's 2006 paper on stratospheric aerosol injection (Crutzen, 2006), some researchers expressed concern that a plausible ‘Plan B’ could reduce incentives to cut emissions — often called mitigation deterrence — and by the Royal Society's 2009 report, avoiding it had become one of the central principles of SRM governance (Jinnah & Dove, 2025).

04Ongoing debate

Still discussed across every intervention strategy

Whether mitigation deterrence actually occurs in practice remains an active area of debate. Empirical studies find the feared effect is often small, absent, or in some cases reversed. The conversation continues across mitigation, CDR, CCS and SRM alike — a shared design question, not a criticism unique to any one approach.

Seen in this broader historical context, moral hazard is a recurring policy concern that has accompanied almost every proposed climate strategy that does not focus primarily on reducing greenhouse gas emissions at their source — from carbon markets to CDR to SRM. Supporters counter that responsible, transparent research clarifies trade-offs and strengthens, rather than weakens, the case for cutting emissions; major assessments have reached broadly the same conclusion.

Critics have raised the concern across a wide range of climate interventions: carbon credits and offsetting, carbon sequestration, carbon capture and storage (CCS), direct air capture (DAC), afforestation and reforestation, soil carbon programs, regenerative agriculture, bioenergy with carbon capture and storage (BECCS), enhanced weathering and solar radiation management (SRM). Whether these concerns materialise in practice remains an active area of debate, and the central question for each approach is whether it could reduce the perceived urgency of cutting emissions at source.

[ [ 07 · The cost of not looking ] ]

The risks of research restraint

A serious discussion of climate cooling has to weigh both sides of the question. If refusing to research cooling plausibly leaves future societies without options in the face of accelerating harm, then declining to look carries its own ethical cost — one that falls most heavily on those least able to bear it.

Philosophers and ethicists have increasingly examined what is sometimes called a counter moral hazard: the risk of foreclosing options that future generations may urgently need, in a warming world we have already largely shaped.

Callies (2019) argues that the responsible position is neither reflexive endorsement nor reflexive rejection, but a rigorous, transparent research program with strong governance — so that if decisions ever have to be made, they are not made in crisis or ignorance (Callies, 2019).

Horton & Reynolds (2016) frame the ethics of climate intervention as a matter of comparative risk: which set of risks — those of researching cautiously, or those of not researching at all — is a fair-minded person willing to accept on behalf of others, including those not yet born? (Horton & Reynolds, 2016)

“Understanding the potential benefits, limitations and risks of climate cooling through rigorous scientific research is a responsible course of action in a rapidly warming world.”
— Adapted from the U.S. National Academies (2021) SRM Research Recommendations
[ [ 08 · Looking forward ] ]

A more complete climate response

Climate cooling research is emerging as an important part of climate science because the world it is being asked to serve has changed. The task now is to build the knowledge, governance and collaboration needed to understand it well — and to use it wisely alongside the other pillars of climate action.

MEER's contribution is deliberately grounded: surface-based cooling that is measurable, reversible, locally governed and scalable — protecting people from dangerous heat today, while adding a complementary tool to a broader strategy for reducing climate risk tomorrow.

What we support

Better science

Open, peer-reviewed research that clarifies what surface cooling can and cannot do.

What we support

Responsible research

Transparent methods, independent review and clear boundaries between study and deployment.

What we support

Evidence-based decisions

Policy informed by measurement, not assumption — with data published openly.

What we support

International collaboration

Shared protocols and shared learning across institutions, countries and communities.

What we support

Complementary solutions

Cooling research designed to strengthen mitigation, adaptation and CDR — never to replace them.

What we support

Protecting communities

Prioritising the people and places most exposed to dangerous heat today.

The goal is a safer, more resilient future — built on rigorous science, honest evidence, and complementary solutions that work together to protect the communities most exposed to a warming world.

How surface cooling works From science to scale
[ A framework for what comes next ]

The Albedo Accord

If the case for cooling research is accepted, the next question is how to conduct it responsibly. The Albedo Accord is MEER's proposed framework for governing surface-based cooling — a shared set of principles for how this work should be done, by whom, and for whose benefit.

The Accord is not a treaty or a technology. It is a civic commitment — a statement of the standards that surface-based cooling should meet before it is deployed at scale: transparency, community consent, open science, and a permanent right to reverse course.

It draws a clear line between the responsible, ground-level cooling work MEER supports and the far riskier proposals for atmospheric geoengineering. The Accord is about surfaces, not the stratosphere.

[ Principles ]

Six commitments that shape every deployment.

Principle 01

Surfaces, not the stratosphere

MEER works at the human scale — rooftops, reservoirs, farms. Not aerosols. Not the atmosphere.

Principle 02

Reversible by design

Every intervention can be undone. No irreversible commitments to the climate system.

Principle 03

Open science, open data

Methods, measurements and outcomes published transparently for independent scrutiny.

Principle 04

Community consent

Free, prior and informed consent from the communities hosting every project.

Principle 05

Complement — never replace — mitigation

Cooling is additional to emissions reduction, never an excuse to slow it.

Principle 06

Equity as first principle

Deployment prioritises the communities most exposed to dangerous heat today.

Read the full Accord

Explore the Albedo Accord in full — principles, governance and the case for adoption.

Read the Albedo Accord
[ [ 10 · Frequently asked questions ] ]

Answers to common questions

[ [ References ] ]

Sources & further reading

A curated bibliography for readers who want to explore the evidence directly. Links open in a new tab.

Continue exploring

Related across MEER

Related projects

Related publications

Related stories

Related MEERTalks

  • MEERTalks→

    Recorded conversations with scientists and partners.

Related science pages

Explore in HeatLens

Related glossary terms

  • PDRC→

    A material that stays cooler than the air even under direct sunlight by radiating heat to the cold sky.

  • Reflective Cooling→

    Cooling by bouncing sunlight away from a surface before it can be absorbed as heat.

  • Radiative Cooling→

    Heat loss from any object by emitting thermal infrared radiation.

  • Reflective Roofs→

    Roofs coated or built with high-reflectance materials so buildings absorb far less heat.

  • Reflective Canopies→

    Overhead structures with a reflective upper surface that shade people and land beneath.

  • Reflective Reservoir Systems→

    Covering water reservoirs with reflective floating panels to cut evaporation and cool the surroundings.