The gas acted like a big duvet, trapping warmth, much of which was stored in oceans.
Emissions had increased since 2000, he said, largely because more fossil fuel was being burned to drive economic growth.
The race was on to limit the overall global temperature rise to 2C.
If that could be done, the weather would still be wild but more manageable.
"It's not yet hopeless but we must act quickly," Dr Tate said.
To limit the rise in temperature, he said carbon dioxide emissions from burning fossil fuels had to be reduced to zero within 30 years. That was "a pretty tough ask" given the procrastination so far.
People's individual efforts would help, but it could not be done without commitment from world leaders, Dr Tate said.
"There's a lot being done, but at a local level. We can all help as individuals, but politicians must lead the charge. One of the big problems is we have politicians who are concerned about their jobs and the next two to three years in power. They're just not willing to make the sorts of changes that are necessary."
The next opportunity for a united global solution will be a meeting of world leaders in Paris in December. They have been asked to arrive with their countries' targets to reduce emissions. New Zealand's goal will be to reduce emissions to 30 per cent below 2005 levels by 2030 - which is well below the European Union target.
"Ours is pathetic. Inviting companies to come here and drill offshore for oil and gas is flying in the face of what the rest of the world is trying to do. It's just absurd," Dr Tate said.
The European Union, by contrast, is on track to limit its emissions and meet the 2C warming limit. The UK has even set milestones for greenhouse gas reductions.
"The hope is that, through discussions in Paris, laggards can be brought into line."
Climate change posed two moral dilemmas. First, it affected the poor more than the wealthy. And second, it affected future generations more than the people alive now.
"We have to increase the living standards of undeveloped countries while reducing the ecological footprint of the developing world."
Dr Tate said there were hopeful signs as the December meeting nears. Nations banded together in the 1970s to limit the sulphur emissions that cause acid rain, then later the chlorofluorocarbons that affect the ozone layer.
The Presbyterian Church has ended its investment in fossil fuels. A Dutch court has ordered its government to cut emissions by 25 per cent. Tokelau is using solar energy instead of imported diesel to run its economy and China, the United States and the European Union have all agreed to limit emissions.