Making the accord legally binding is not enough to guarantee the world keeps warming within agreed limits. That will take much more - not least ending our reliance on fossil fuels

Ratifiying the Paris agreement will be a major step but must be the first of many

In a rare show of international unity, more than 30 countries this week declared their plans to translate into national laws the Paris agreement on climate change.

As a result, by the end of this year, or soon after, the accord should come into effect and become binding under international law.

This is a major step. It will be the first time since 1992 that a global agreement on climate change has been internationally accepted (the Kyoto protocol, signed by the White House in 1997, was famously stymied by the refusal of the US Congress to ratify it), and the first time in history that rich and poor countries have faced the same obligations to tackle global warming.

Ratification may seem a small step, given that the agreement was passed by every one of the 195 United Nations member states last December. But it is important because it gives full legal standing to the document. That makes it harder for any government to row back on the Paris commitments.

The most obvious potentially recalcitrant nation is the US, the world’s second biggest emitter of greenhouse gases, where the presidential contender Donald Trump has vowed to unpick the agreement if elected this November. But other countries are also in danger of reneging. Russia was always a reluctant member, Nicaragua showed signs of trying to stop the agreement while the ink was still wet, and Australia’s volatile politics on climate change could yet cause a U-turn on the part of its government.

Paris will enter into force if 55 countries, and enough countries to account for 55% of global emissions, ratify its contents. The former target will be met if the nations that have publicly agreed to ratify now do so, and the latter will soon be met if the EU, as promised, takes on its responsibilities in a bloc-wide agreement, expected early next year.

It is also important to recall the history of climate change treaties. The failure of the US to ratify, despite presidential approval, and Russia’s plodding acceptance, meant that the 1997 Kyoto protocol only became legal in 2005. By then it was largely academic, as the world had moved on to begin negotiations on a new global settlement on climate change. The world had also moved on in terms of emissions, as China was confirmed as the world’s second biggest emitter – and is now the biggest.

Kyoto placed quantified commitments on all developed countries to reduce their greenhouse gas emissions. Paris does not. Although nearly all of the world’s countries – including the biggest emitters, developed and developing – submitted plans before the Paris conference to cut or curb their emissions, those plans are not legally binding and will not be even when the accord enters into force.

The only legally binding commitment is to limit global warming to no more than 2C above pre-industrial levels, with an additional “aspiration” to take even more drastic action to limit warming to 1.5C, which if adhered to could save the world’s low-lying islands from inundation.

Quantified emissions curbs up to 2020 – not legally binding but set out publicly – were also agreed in 2009, at the much-derided Copenhagen conference on climate change, and those commitments still stand.

More importantly, the geopolitical landscape has been transformed in the 20-plus years in which the world has been discussing a global response to climate change. China, which carried no obligations under Kyoto, is now the world’s biggest emitter and soon to be the biggest economy. Developing nations are also now the biggest sources of the stock of carbon in the atmosphere, outpacing the richer countries responsible for “historic” emissions before the 1990s.

What should we take from the Paris pact? First, recognise the limitations of what can be considered legally binding under international law. While nations were willing to agree to limit global warming, they were not willing to take on binding targets on reducing emissions, of the kind that were stipulated at Kyoto. It is now clear, after more than 20 years of international negotiations, and a changing pattern of which nations contribute most to the stock of carbon dioxide that is warming the planet, that even supposedly binding agreements do not guarantee reductions in emissions.

That depends on countries delivering on their pledges to curb carbon production, which in turn depends on their internal politics. No international treaty, legally binding or not, can force countries to limit emissions if they are not willing to do so.

So, although the Paris agreement is an important step, it will not be enough to guarantee that warming will not exceed scientific advice. Following through on the goal of limiting climate change will require much more: a reversal of the current reliance on fossil fuels in favour of low-carbon forms of energy production; businesses to alter their practices so that their activities produce less carbon; individuals to alter their behaviour; and finding ways to cope with a growing population of people who, rightly, wish to enjoy the fruits of modern prosperity without destroying the aspirations of their children to do the same.

The Paris agreement acknowledged that climate change is a global problem that will require concerted global action. It is not, in itself, a solution to that problem. But it provides a way forward that can be built into a solution. If we want it.