Attenborough was speaking in front of the U.K. Parliament's Business, Energy and Industrial Strategy Committee to discuss a range of issues related to climate change, including the ecological impact of global warming and the benefits of a transition to a low-carbon economy.
"No one has done more to show the impact of man-made climate change on our planet", said Reeves.
He first visited the Australian landmark in the 1950s, describing it as a "multitude of fantastic, attractive forms of life".
He also mentioned the dying Great Barrier Reef in his rant, saying he remembers visiting the then-thriving reef in the 1950s.
But upon his return 10 years ago, he said: "Instead of multitudes of wonderful forms of life, I was struck by how it was bleached white because of the rising temperatures and increasing acidity of the seas".
Not everyone may share his enthusiasm about the beauty of the reef but Sir David said the system was "crucial" to the world. We are living in a climate emergency which affects each and every one of us - whether we like it or not.
Asked about claims from climate change deniers that people were "overpanicking", he singled out Australia and the United States as places where there were still people in positions of power who were sceptics. If the world climate change goes on, it is going to be facing huge problems with immigration.
"Nobody thought that human beings could change the climate and we are... and what is worse is that we are changing the climate in a way that is irreversible".
"But both Australia and America those voices are clearly heard".
However, Sir David did not think the voice of criticism or disbelief should be "stamped on".
We can not be radical enough in dealing with the issues that face us at the moment.
Attenborough took aim at the U.S. and Australia as countries where climate science denial was particularly strong.
"Dealing with the problems means changing our lifestyles", he added.
The famous presenter's comments came just months after the federal election, where the issue of climate change divided independents, the ALP and the Coalition.
"I think our record has been pretty good", he said.
"That is a source of great comfort in a way, but also a justification of reality that these young people now are recognising that their world is what is the future", he said.
Attenborough said he was hopeful we are on the cusp of great social change thanks to young people who are taking a stand on climate change, comparing the attitude shift to the human rights fight against slavery.
A report by Berlin-based science and policy institute Climate Analytics found planned coal and gas expansions could push Australia's share of emissions higher over the next decade.