Scientists warn of 'abrupt and irreversible climatic shifts'
Updated
Researchers are warning the planet is facing a growing risk of abrupt and irreversible climatic shifts unless carbon emissions are reduced.
The stark caution is contained in a document published overnight. The report says greenhouse gas emissions and other critical indicators are at, or near, the upper limits forecast by the UN's Intergovernmental Panel on Climate Change two years ago.
Presenter: Sabra Lane
Speaker: Professor Will Steffen, head of the ANU's Climate Change Institute
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WILL STEFFEN: The climate system is now moving out of the envelope of variability of which our civilisations have developed. In some aspects it's moving right near the upper range of earlier projections. This gives us a sense of urgency. A good example of that is sea level rise which is moving right at the upper level of the projections we have had around now for about 20 years.
It's a pretty fundamental parameter because it is related partly at least to how fast the oceans are warming. That's where about 90 per cent of the extra heat is going so we have a very good indicator now that the climate shift, the system is shifting pretty definitively and pretty rapidly.
SABRA LANE: The report also talks about evidence pointing towards the very real possibility of triggering tipping points caused by human made climate change. What does that mean? What are you talking about? Are you talking about the Great Barrier Reef here or ...?
WILL STEFFEN: Yes and we are talking about other systems like that. Basically a tipping point means that a system is not going to respond in a nice smooth way to increased CO2 in the atmosphere or increased temperature.
You could see temperature rise, temperature rise, nothing happening to a system; an example being the Indian monsoon for example. And then with a small additional increase in temperature it may flip to a much drier state.
So basically a tipping elements means you can push and push and push a system, a bit like a canoe. If you are starting to tip over in a canoe, it always comes back until you just reach that critical point and then you tip over.
Natural systems do this. I will give you three examples. One is the Indian monsoon in which about a billion or so people depend for their water supplies. Another one is the Greenland ice sheet and indeed most big polar ice sheets. And a third one indeed would be something like the Great Barrier Reef - a big natural ecosystem which is resilient to a point but once you pass that point then it will change very quickly.
SABRA LANE: How long has the world got to start reducing emissions?
WILL STEFFEN: If we want to keep temperatures below two degrees which is an often quoted guardrail, we pretty much need to see our emissions peak within the next six to 10 years and then drop very quickly after that.
SABRA LANE: How would you characterise this report?
WILL STEFFEN: Yes, I think I could paraphrase the Prime Minister of Denmark who was in the final session who looked at this and said alright, this is giving me a sense of urgency, this is giving me a sense that we have to come out of Copenhagen in December with a widely agreed road map that includes the big developing countries like China and India as well as the major players in the industrialised world like the United States.
We have to get to that level of remit. We can't wait for another round of negotiations. So his bottom line message was he took the science on board and said now is the time we have got to move.
