Scott Morrison has used his address to the United Nations to strongly defend the government’s performance on climate change, declaring defiantly Australia was “doing our bit” and “we reject any suggestion to the contrary”.

In a speech concentrating on Australia’s response to “the great global environmental challenges” Morrison emphasised dealing with plastic waste.

“To protect our oceans, Australia is committed to leading urgent action to combat plastic pollution choking our oceans, tackle over-exploitation of our fisheries, prevent ocean habitat destruction and take action on climate change,” he said.

Meanwhile, a new report from the Intergovernmental Panel on Climate Change, released on Wednesday, calls for urgent climate change action “to address unprecedented and enduring changes in the ocean and cryosphere”.

The IPCC says that with the increase in temperature that has already occurred “the ocean is warmer, more acidic and less productive. Melting glaciers and ice sheets are causing sea level rise, and coastal extreme events are becoming more severe”.

With much international attention on the Great Barrier Reef, Morrison declared the reef was “vibrant and resilient and protected under the world’s most comprehensive reef management plan”.

He said that on climate change Australia was “taking real action … and getting results”, and attacked critics.

“We are successfully balancing our global responsibilities with sensible and practical policies to secure our environmental and economic future.

"Australia’s internal and global critics on climate change willingly overlook or ignore our achievements, as the facts simply don’t fit the narrative they wish to project about our contribution.”

Read more: View from The Hill: What might Lily and Abbey say to Scott Morrison about Greta Thunberg?

Morrison’s speech came in the wake of considerable criticism of his failing to attend the UN leaders summit on climate at the start of the week.

Reeling off facts and figures on Australia’s performance, the Prime Minister told the General Assembly, “this is a credible, fair, responsible and achievable contribution to global climate change action. It represents a halving of emissions per person in Australia, or a two thirds reduction in emissions per unit of GDP”.

Australia had the world’s highest per capita investment in clean energy technologies, he said, and one in five households had rooftop solar systems.

Referring to the Australian government’s decision not to put more money into the Global Green Climate Fund, Morrison said it preferred to invest directly, targeting Pacific island countries.

In sum, Australia was taking “significant and comprehensive action … in response to the world’s greatest environmental challenges”.

On the push by young people on climate issues - highlighted last week by the school strikes and this week by Swedish activist Greta Thunberg’s much publicised address to the summit - Morrison said that like other leaders he received many letters from children about their future.

“I deeply respect their concerns and indeed I welcome their passion, especially when it comes to the environment.

"My impulse is always to seek to respond positively and to encourage them. To provide context, perspective and particularly to generate hope.

"To focus their minds and direct their energies to practical solutions and positive behaviour that will deliver enduring results for them.

"To encourage them to learn more about science, technology, engineering and maths – because it’s through research, innovation and enterprise that the practical work of successfully managing our very real environmental challenges is achieved.”

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The passion and aspiration of the young must be respected and harnessed, he said. At the same time “we must guard against others who would seek to compound or, worse, facelessly exploit their anxiety for their own agendas. We must similarly not allow their concerns to be dismissed or diminished as this can also increase their anxiety.

"Our children have a right not just to their future but to their optimism.

"Above all, we should let our children be children, let our kids be kids, let our teenagers be teenagers - while we work positively together to deliver the practical solutions for them and their future.”

Before delivering his speech Morrison visited an Australian company’s recycling facility in New York.

At a press conference there, he told reporters his talks had reinforced the fact “that we’ve just got to keep working hard to get our energy costs down” so they could compete globally.

“I keep coming back to this issue of gas and looking at all the alternatives on the table.” he said.

There was more work to be done on dealing with electricity prices.

“It’s a constant challenge”, he said, while shifting a lot of the weight to the state governments.

The federal government wasn’t the primary government with the impact on electricity prices, he said.

“We all know that it’s the state governments who basically are in charge of the assets and resources access that principally determines these costs and the cost of the system and the utilities.

"They also determine whether you can get gas out from under people’s feet. Now the reason electricity prices are as low as they are in the United States, and particularly down south, is because of access to gas. We’ve got heaps of gas and it’s being kept under people’s feet. So that’s something we’ve got to change,” he said. The states needed to change the rules.

Michelle Grattan does not work for, consult, own shares in or receive funding from any company or organisation that would benefit from this article, and has disclosed no relevant affiliations beyond their academic appointment.