As claims and counterclaims swirl about the health of the Great Barrier Reef, it can be difficult to know what to believe. A good starting point is listening to Terry Hughes, the director of the ARC Centre of Excellence for Coral Reef Studies, and listed last year by the journal Nature as one of the 10 people who matter most in science.

Professor Hughes, who regularly surveys the reef, last week stunned his Twitter followers by saying 49 per cent of shallow corals had died after two summers of bleaching.

This figure was given preliminary endorsement by Russell Reichelt, the chief executive of the Great Barrier Reef Marine Park Authority. He noted there had also been an increase in cover in the south in recent years, but added: "It is difficult to say this without sounding like I don't think the problem is serious. I certainly do."

If anything, serious is an understatement. The loss of half of the reef's shallow water corals is a global-scale catastrophe. It may have potentially serious ramifications in the years ahead for about 70,000 people who rely on the reef for their livelihoods.

It is linked to inflated water temperatures that scientists have tied to escalating greenhouse gas emissions. As The Age revealed, an expert panel advising the government on how to implement its plan to protect the reef says it must be re-drawn to include a focus on cutting. We agree. So far the Turnbull government has demurred.

This is indicative of a broader disconnect in the government about climate change. It says the United Nations process that led to the Paris accord is the best place to address the issue, including protecting the reef from it. Yet the best evidence suggests the emission reductions targets pledged in the French capital are nothing like enough to achieve this goal.

Of course, Australia alone cannot tackle climate change. But it can hardly expect other countries to do what is necessary if it doesn't itself. Its emissions target of a 26-28 per cent below 2005 levels by 2030 is a step up from previous commitments, but not enough for Australia to play its part in addressing the problem. Malcolm Turnbull and Environment Minister Josh Frydenberg have acknowledged the target will need to be increased, and analyses have suggested more could be done at relatively little cost. It is hoped that will be included in the review of climate policies currently under way. 

The review must also address the more glaring issue: the lack of a coherent policy that can deliver even the current targets. When the government abolished the carbon price scheme in 2014, it put the "direct action" emissions reduction fund at the centre of its own response. Three years on, $2.23 billion has been spent from the budget for little obvious impact. An analysis by the Parliamentary Budget Office commissioned by the Greens found meeting the 2030 target using the fund alone would cost more than $23 billion – an unrealistic figure in budget-constrained times.

The government says the analysis is also unrealistic as the fund is only part of its response to climate change. But the other policies Mr Frydenberg cited – a National Energy Productivity Plan, reducing hydroflurocarbons, and a renewable energy target that ends in 2020 – are complementary policies, not a central measure to drive change. And it continues to support emissions intensive projects, such as the proposed Adani coal mine.

The centre of the government's response needs to be a carbon pricing scheme to encourage the shift from coal to cleaner practice. The new head of the Australian Energy Market Commission, Anne Pearson, has added her voice to the business leaders and analysts who say an emissions intensity scheme is the most effective response. It's time the government started to listen.

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