Australia is expected to experience a 6C average temperature rise on its hottest days and lose many reptile, bird and mammal species as well as the renowned wetlands of Kakadu by the end of the century, the latest Intergovernmental Panel on Climate Change report reveals.

IPCC figures show that Australia will experience an average overall increase of 2C by 2065, with that figure slightly lower at the coast. Beyond that, the temperature is expected to rise another 3C-4C by 2100.

The number of days that don't fall below 20C is projected to rise to 100 a year, with most of these warmer days in the north and on the east coast.

Rainfall patterns are set to change, with annual precipitation, humidity and cloud cover predicted to decrease over most of Australia. But for north Australia and many agricultural areas, rainfall is predicted to get heavier. Soil moisture will decrease, mostly in the south of the country. These changes will have a significant impact on many aspects of life, according to the comprehensive report, which is released every six years after input from hundreds of scientists around the globe. In Australia, an increase in the frequency and intensity of heatwaves is expected to lead to more heat-related deaths, while warmer temperatures, changing rainfall and an influx of pests will "negatively impact" many temperate crops, such as fruit and nuts. Rising sea levels will affect coastal developments and risk causing "extensive loss" of wetland habitat through saltwater intrusion in the celebrated Kakadu national park in the Northern Territory. A 2C-4C rise in average temperatures will wipe out 21%-36% of Australia's butterflies, while the loss of nearly half of appropriate habitat in Queensland will spell doom for 7%-14% of reptiles, 8%-18% of frogs, one in 10 birds and 10%-15% of mammals. Australia has warmed by 0.4C-1.25C since 1901, with most of the rise taking place in the centre of the country. Globally, there has been a 0.89C rise in average temperatures since the start of the 20th century, the IPCC findings state. There is now a 95% certainty that humans, through the burning of carbon intensive fuels, are responsible for most of the warming.

To keep average global temperature rises below 2C – the internationally agreed upper limit of warming – greenhouse gas emissions will need to be cut by 10% a year, according to the report.

In a statement released after a laborious process where the IPCC report was trawled over line by line by 110 nations, the UN body said governments had been handed a "firm mandate" to act on climate change.

"The report confirms that the planet is heating up, sea level rise is accelerating, the rate of Arctic Sea ice retreat has doubled, the melting of glaciers and ice sheets is happening faster, and the oceans are acidifying," it said.

"This report shows that the science on climate change is clear. The debate about who is responsible is over. People rightly demand that governments tackle the climate risk posed to our communities and economies."

Climate scientists in Australia involved in the report echoed these sentiments.

"In many ways the certainty of human influence can be 95% or 97%, it doesn't make any difference," Andy Pitman, a review editor of the IPCC report and director of the ARC Centre of Excellence for Climate System Science, told Guardian Australia.

"In what other decision-making process do you need certainty above 95%? This is way, way beyond the realms of doubt. There is no excuse for a lack of policy response. There may have been an argument around 1990, but not since 2001 and certainly not now."

The IPCC report is set to address the issue of a "warming pause" over the past 15 years, which has been seized upon by some climate change sceptics as evidence that warming has been exaggerated by erroneous modelling. The plateau in temperature increase is to be attributed to a variety of factors, including an increase in aerosol use and the storage of more than 90% of accumulated heat in the deep oceans, rather than on the surface. "There has been a double-dip La Niña, huge ocean uptake, a solar minimum and aerosol particles," Pitman said. "When those things aligned in the past, we see a three- or four-tenths of a degree of cooling. This time, it's plateauing – so the question is why didn't it cool back to the levels of 1990? That's a considerable concern. "A number of papers say to expect decades of cooling against a long-term warming trend. The significance of climate change not capturing the last 15 years is the same as Usain Bolt swimming a slow 100m. It's utterly irrelevant." Professor David Karoly, a fellow of Melbourne University and another reviewer of the report, told Guardian Australia that the human influence over warming was "now beyond reasonable doubt" and placed the onus on a greater response to cutting emissions. "For the first time, the IPCC report will look at the role of the carbon budget and the cumulative effect of burning carbon that's linked to dangerous climate change," he said. "The longer we delay, the harder it is to avoid dangerous climate change."

The IPCC has set this "carbon budget" at 1 trillion tonnes of emissions, saying the world has already burned through half of this and will have exhausted the budget within 30 years if no further action is taken.