Tomorrow, world leaders and diplomats will converge on the United Nations’ New York headquarters to sign the Paris Agreement on climate change. It will be the largest UN signing event in history, with representatives from at least 162 countries, including more than 60 heads of state, on hand to sign the historic deal that was struck last December.

Signing is just the first step. Nations then have to follow through by ratifying the agreement. Only when 55 countries, representing at least 55% of world greenhouse emissions, have signed and ratified the agreement will it become binding under international law.

Such is the eagerness among the international community to sign and ratify the Paris Agreement that it is quite possible it could enter into force this year, rather than in 2020 as was initially expected.

As 2016 continues to smash global heat records, there is a renewed sense of urgency among almost all governments. They now acknowledge that greenhouse emissions must be reduced rapidly if there is any hope of meeting the Paris Agreement’s goal of keeping global warming well below 2℃.

Australia’s government has confirmed that it will be represented at the ceremony, although it will be Environment Minister Greg Hunt rather than Prime Minister Malcolm Turnbull who will join world leaders in inking the deal.

Australia’s track record

Australia has signed previous climate treaties, but it has a mixed record in following through with its commitments.

The Keating government supported the Rio Earth Summit in 1992. In the same year, it signed and ratified the UN Framework Convention on Climate Change. That agreement gave rise to the UN climate regime of which the Paris Agreement is now the most important component.

In 1997, the Howard government negotiated and signed the Kyoto Protocol, in the process winning major concessions that allowed Australia to increase its emissions rather than reduce them.

Despite this sweetener, John Howard refused to take the logical step and render Kyoto legally binding by ratifying it. The Kyoto Protocol only entered into force in 2005, after Russia ratified the treaty. It was not until 2007, following the election of the Rudd government, that Australia finally ratified Kyoto.

In 2011 the Gillard government introduced an emissions trading scheme (with an initial fixed carbon price) to ensure Australia could meet its Kyoto commitments (and deliver deeper cuts over time, as by itself Kyoto has achieved minimal emissions reductions). But the Abbott government repealed this measure in July 2014 and replaced it with the Direct Action policy. This policy remains a work in progress and has not locked in the necessary emissions cuts to keep Australia’s goals within reach.

Australia’s actions since 2013 are clearly against the international tide. According to the World Bank, 40 nations and 23 subnational jurisdictions have adopted or are planning to adopt carbon prices.

The Turnbull government’s active and supportive participation in last year’s Paris climate negotiations signalled that, on the international plane at least, some bipartisanship has returned to Australia’s climate policy. The same cannot be said of the domestic front, where the major parties are still at loggerheads on the climate challenge.

Opposition Leader Bill Shorten has pledged that a Labor government would reintroduce an emissions trading scheme if elected this year. But the Coalition government remains implacably opposed to any price on carbon. This is despite the fact that Turnbull himself was a strong supporter of carbon pricing and previously staked (and lost) his leadership of the Liberal Party on emissions trading in 2009. Even Howard proposed a comprehensive emissions trading policy in the dying days of his government in 2007.

Tricky times

This is a major problem because without agreement across political lines, Australia could be signing a treaty with which it cannot comply.

Australia is the world’s 13th-largest greenhouse emitter and the highest per capita emitter in the OECD. Now, because of the abolition of the carbon price, its emissions are rising for the first time in a decade.

Australia looks set to overshoot even its modest target of reducing emissions by 26-28% by 2030 relative to 2005 levels. And as commitments under the Paris Agreement will become stricter over time, with the deal requiring countries to ramp up their climate pledges every five years, Australia will be in an increasingly difficult and embarrassing position of having made promises it cannot keep.

This may set the scene for dithering by the Turnbull government, in much the same way as the Howard government held out against ratifying the Kyoto Protocol for a decade before finally proposing a climate policy when electorally it was already too late.

This year is off to a scorching start. Globally, February was a record-breaking 1.35℃ above average and March beat that record as soon as it was set. The effects are being felt from the polar regions, where the melting of the Greenland ice sheet is off the charts, to the tropics and subtropics, where record warm waters have bleached the Great Barrier Reef.

We know that to make a meaningful contribution to combating climate change, Australia needs a credible path to net zero emissions by 2050. To do this the Turnbull government must match its international commitments with effective laws and policies at home.

Legislating Australia’s climate targets, setting a national cap on emissions, and pricing carbon pollution are vital if Australia’s signature on the Paris Agreement is to mean anything at all.