In August, Reform UK deputy leader Richard Tice posed a challenge that deserves a serious answer.
Speaking about climate change and net zero, Tice questioned where the evidence was that net zero would stop climate change. He acknowledged that climate change was real, but argued that climate has always changed and suggested we might be better adapting to it rather than thinking, in his words, “arrogantly” that we can stop it.
There is nothing unreasonable about asking for evidence.
Governments are proposing profound changes to the way we generate electricity, heat buildings, manufacture products and move people and goods. Those changes cost money. Some technologies will succeed better than others. Some policies will prove effective and others may turn out to be expensive mistakes.
We should be able to challenge all of them.
But Tice’s question raises another, more fundamental one.
Can humans recognise that something we are doing is altering the atmosphere, understand the mechanism, coordinate action internationally and then measurably change what happens next?
For that, we do not have to rely entirely on projections of what might happen in 2050.
We have already conducted something of a real-world experiment.
We call it the Montreal Protocol.
When we discovered we were changing the atmosphere
For much of the twentieth century, chlorofluorocarbons, better known as CFCs, looked like extremely useful chemicals.
They were stable, non-flammable and effective. They found their way into refrigerators, air-conditioning systems, insulation foams, industrial processes and aerosol cans.
Unfortunately, the same stability that made them useful allowed them to survive long enough in the atmosphere to eventually reach the stratosphere.
There, ultraviolet radiation could break them apart, releasing chlorine atoms capable of destroying ozone molecules.
This mattered because the stratospheric ozone layer protects life on Earth from harmful ultraviolet radiation.
Scientists warned during the 1970s that CFC emissions could damage that protection. Then, in the 1980s, measurements over Antarctica revealed severe seasonal ozone depletion.
The “ozone hole” became one of the defining environmental stories of the decade.
CFCs were once commonplace in aerosols, refrigeration, foams and other everyday products. Their widespread use ultimately helped trigger one of the world’s most successful examples of coordinated environmental action.
It presented governments with a remarkably difficult problem.
The chemicals involved were economically useful. The damage was occurring kilometres above our heads. No country could solve the problem within its own borders because the atmosphere does not respect national boundaries.
There was uncertainty over exactly how quickly the problem would develop.
Doing nothing would have been an option.
Humanity chose something else.
Montreal turned science into action
The Montreal Protocol on Substances that Deplete the Ozone Layer was agreed in 1987 and entered into force in 1989.
Its significance wasn't simply that governments signed another international environmental agreement.
The agreement created a mechanism through which action could actually happen.
Countries progressively restricted and phased out ozone-depleting substances. Scientists continued monitoring the atmosphere. Regulations were strengthened as the evidence developed. Industry invested in alternatives. Refrigeration technology changed. Manufacturing processes changed. Products changed.
Developing countries were provided with financial and technical assistance to help them make the transition.
And importantly, the agreement evolved.
It did not require governments in 1987 to possess perfect knowledge of every technology that would eventually replace CFCs. It established a direction and then allowed regulation, science and innovation to respond.
The results are measurable.
According to the UN-backed Scientific Assessment Panel, nearly 99 per cent of banned ozone-depleting substances have now been phased out.
The ozone layer is recovering.
If current policies remain in place, ozone is expected to return to approximately 1980 levels around 2040 across most of the world, around 2045 over the Arctic and around 2066 over Antarctica.
We therefore have something unusually valuable in environmental policy.
A before.
An intervention.
And an observable after.
From scientific discovery to international agreement, regulation and innovation, the Montreal Protocol shows how coordinated global action turned an atmospheric problem towards recovery.
What does that actually prove?
This is where we need to resist the temptation to make the ozone story prove more than it does.
The Montreal Protocol does not prove that net zero will work exactly as currently envisaged.
It does not prove that every heat pump, electric vehicle subsidy, wind farm or carbon tax represents good policy.
It certainly does not demonstrate that climate change can simply be “fixed”.
What it demonstrates is narrower.
Human activity was altering the atmosphere.
Science identified the cause.
Governments cooperated internationally.
Regulation reduced the substances responsible.
Industry developed alternatives.
And atmospheric measurements subsequently showed the expected response.
That matters when we ask whether coordinated human intervention can make a meaningful difference to a planetary environmental problem.
The evidence suggests that it can.
Indeed, the Montreal Protocol did something else.
Many ozone-depleting substances are themselves extremely powerful greenhouse gases. Removing them, therefore, didn't just protect ozone. It also reduced the amount of warming that would otherwise have occurred.
UN-backed assessments estimate that the Montreal Protocol is avoiding substantial additional warming compared with a world in which ozone-depleting substances had continued increasing unchecked.
So the intervention did not merely change industrial behaviour.
It changed the atmospheric outcome.
But carbon dioxide is a much harder problem
At this point, anyone sceptical of the comparison can make an entirely reasonable objection.
CFCs are not carbon dioxide.
The ozone problem was, in several important respects, considerably easier to tackle.
Although CFCs were widely used, they represented a relatively defined group of chemicals serving identifiable purposes. Alternative substances and technologies could be developed.
Replacing the refrigerant inside a refrigerator does not require restructuring the global economy.
Carbon dioxide is different.
Fossil fuels have powered industrial development for more than two centuries. They remain deeply embedded in electricity generation, transport, heating, agriculture, aviation, shipping, steel, cement, chemicals and manufacturing.
We cannot simply identify one chemical, prohibit it and declare the job finished.
Climate change also involves multiple greenhouse gases, huge differences between national economies and difficult questions about who pays for the transition.
A rapidly developing country seeking affordable energy understandably approaches the problem differently from a wealthy country whose industrial development was largely built using fossil fuels.
The Montreal Protocol is therefore not a blueprint for net zero.
But dismissing it because the problems are different would miss the more useful lesson.
Instead, we should ask: what actually made Montreal work, and can any of those ingredients be replicated?
Five things Montreal got right
The first was credible science.
Policy followed an increasingly strong understanding of the mechanism causing the problem. Monitoring then continued after regulation was introduced, allowing scientists to determine whether intervention was working.
That same principle should apply to climate policy. Measure the problem, model the likely consequences, implement interventions and then measure whether they deliver.
The second was international cooperation.
No country could repair the ozone layer independently. Governments recognised that unilateral action would be insufficient and established a framework within which countries could move broadly in the same direction.
That is particularly relevant when discussing Britain's contribution to climate change.
The UK acting alone cannot determine the global temperature.
But neither could Britain acting alone have repaired the ozone layer.
Global environmental problems inevitably create the uncomfortable requirement for global cooperation.
The third ingredient was regulation.
Governments didn't simply ask consumers to use fewer CFCs. They progressively changed the rules governing their production and use.
Fourth was innovation.
Industry was given both the requirement and the incentive to develop alternatives.
And fifth was practical support for transition.
Countries did not all have identical resources or capabilities, so mechanisms were created to help poorer countries adopt alternatives.
None of those principles guarantees that climate policy will succeed.
But they provide a considerably more useful starting point than either assuming every net-zero policy must work or assuming nothing we do can make a difference.
Problem-solving is what humans do
There is a temptation when confronted by something as vast as climate change to see its complexity as evidence of its impossibility.
Human history suggests caution about that conclusion.
Consider some much more familiar examples.
We learned that contaminated water was spreading disease, so we developed sewerage systems, drinking-water treatment and public-health regulation.
We discovered that certain diseases were caused by microorganisms and developed vaccines and antibiotics.
We learned to predict weather, build flood defences, generate electricity, cross oceans in hours and communicate almost instantaneously across the planet.
None of these achievements happened because somebody discovered a single perfect solution.
They emerged from combinations of scientific understanding, engineering, investment, regulation, experimentation and, sometimes, failure.
Complex environmental problems rarely have a single solution. Science, engineering, investment, regulation and international cooperation all played a part in tackling ozone depletion, and the same combination will be needed as we respond to climate change.
That does not mean climate change will inevitably be solved.
There is nothing inevitable about progress.
But our capacity to solve complex problems is one of the defining characteristics of human society.
The pragmatic response to a difficult problem should therefore not be blind optimism.
Nor should it be resignation.
It should be to identify what works, discard what doesn't, improve the technology and keep measuring the outcome.
Montreal provides an example of precisely that process.
Don't ask individuals to solve a systems problem
There is another lesson from the ozone story that climate policy sometimes forgets.
People did not repair the ozone layer by becoming experts in atmospheric chemistry.
Consumers didn't stand in electrical retailers comparing the ozone-depletion potential of competing refrigerators.
The system changed around them.
Governments established standards. Manufacturers changed products. Engineers developed alternatives. International agreements provided direction.
Eventually, the environmentally preferable option became the ordinary option.
That principle has considerable relevance to net zero.
If cleaner electricity is available through the grid, households reduce emissions simply by switching on their appliances.
If new homes require less energy to remain comfortable, their occupants benefit without constantly making environmental calculations.
If public transport is reliable, convenient and affordable, choosing it becomes easier.
If technologies become cheaper and better, adoption becomes less dependent upon environmental conviction.
Perhaps the most successful environmental policies are ultimately those we stop noticing.
They make the better choice normal.
Adaptation and mitigation are both necessary
Tice is right about one important point: we need to adapt to a changing climate.
For WaterMatters, that is particularly obvious because many of the consequences arrive through water.
Long dry periods put pressure on reservoirs, rivers and groundwater. Higher temperatures increase water demand. Intense rainfall can overwhelm drainage systems. Agriculture increasingly needs to cope with both too little and too much water.
Britain needs more resilient water infrastructure.
That means new water resources, reduced leakage, better drainage, rainwater harvesting, sustainable drainage systems, more resilient landscapes and homes and infrastructure designed for changing conditions.
But adaptation and mitigation answer different questions.
Adaptation asks:
How do we cope with the change that is happening?
Mitigation asks:
How much further change can we avoid?
We need to do both.
The amount of adaptation required in 2050 and beyond will depend partly upon how successful the world is at reducing emissions before then.
So, where is the evidence?
Richard Tice is entitled to ask where the evidence is.
We all should.
If a government proposes spending billions of pounds on a particular climate policy, it should demonstrate why that intervention represents an effective use of money.
If technologies don't deliver, change them.
If targets are unrealistic, challenge them.
If policies impose disproportionate costs on people who cannot afford them, redesign them.
Climate policy should not be protected from scrutiny simply because its intentions are good.
But evidence works both ways.
When scientists discovered that CFCs were damaging the ozone layer, humanity faced an atmospheric problem that no individual country could solve.
Governments cooperated.
Regulations changed.
Businesses innovated.
Technology adapted.
Consumers moved to different products.
Emissions fell.
And decades later, measurements show that the atmosphere is responding.
Climate change is vastly more complicated. The Montreal Protocol doesn't tell us how to decarbonise steel, aviation, heating or electricity. It doesn't tell us which British net-zero policies represent value for money. And it certainly doesn't guarantee that international cooperation will succeed.
What it does demonstrate is that coordinated action, supported by science, regulation, innovation and international cooperation, can change the trajectory of a global environmental problem.
That is not an argument for complacency or unquestioning faith in net zero.
It is an argument for problem-solving.
Human beings have spent our history confronting problems that initially appeared beyond us. Sometimes we have failed. Sometimes we have made matters worse. But sometimes science, engineering and cooperation have allowed us to achieve things that previous generations would have considered impossible.
The ozone layer is one of those occasions.
So perhaps the most useful response to the question “Where is the evidence?” isn't indignation.
It is to point upwards.
The evidence is already there.
