The Climate Commission has just released its first report (download from here) entitled The Critical Decade: Climate science, risks and responses. The report is clear, simple and succinct with excellent illustrations.
If you want to cut to the chase, the message is encapsulated in the highlighted graph. If we, the world, start to reduce emissions now (impossible) by 3.7% a year, we can get away with an eventual reduction of about 85% by 2050. If we start reducing emissions in 2020 we’ll need to reduce by 9% each year (impossible). If we start in 2015 we can get away with reductions of 5.3% per year (barely possible). But we will have to reach zero net emissions by 2040 and then go negative. Is that possible? Barely, if at all, I suspect.
If the graph looks familiar, it is in fact an adaptation and updating of Figure 3 in the post Climate crunch: the fierce urgency of now from 4 January, 2011. That was adapted from an earlier post of November 2009, so LPers have been forewarned.
But look! The reductions required with a 2020 start were 6% each year back then. Now it’s 9%. I assume this reflects the latest science.
The key messages are as follows:
- 1. There is no doubt that the climate is changing. The evidence is overwhelming and clear.
2. We are already seeing the social, economic and environmental impacts of a changing climate.
3. Human activities – the burning of fossil fuels and deforestation – are triggering the changes we are witnessing in the global climate.
4. This is the critical decade. Decisions we make from now to 2020 will determine the severity of climate change our children and grandchildren experience.
“This decade is critical. Unless effective action is taken, the global climate may be so irreversibly altered we will struggle to maintain our present way of life.” “Without strong and rapid action there is a significant risk that climate change will undermine our society’s prosperity, health, stability and way of life.”
The longer we leave it the more difficult and costly it becomes.
The report has three chapters, reflecting the subtitle:
- Developments in the science of climate change
- Risks associated with climate change
- Implications of the science for emissions reductions
I won’t give a summary of these, rather I’ll just highlight some bits on the way through.
The report tells us that:
we know beyond reasonable doubt that the world is warming and that human emissions of greenhouse gases are the primary cause.
It is unapologetic about the IPCC report:
The IPCC AR4 has been intensively and exhaustively scrutinised, including formal reviews such as that by the InterAcademy Council (2010), and only two peripheral errors, both of them in the WG 2 report on impacts and adaptation, have yet been found (in a publication containing approximately 2.5 million words!). No errors have been found in any of the main conclusions, nor have any errors been found in the 996-page WG 1 report, which describes our understanding of how and why the climate system is changing. The IPCC AR4 WG 1 report provides the scientific input to the development of climate policy.(Emphasis added)
There is a short note telling us that we have 1,700 billion tonnes of carbon in the form of methane locked up in permafrost, twice as much as is present in the atmosphere now. One study tells us that about 100 billion tonnes are vulnerable to thawing this century.
It could be worse and going above the so-called 2C guardrail raises the chance that it will be. The stuff is leaking now. The problem as I see it is that it will continue to leak until we get the temperature down from where it is now, something that will take centuries. Since we have to go net negative in emissions before mid-century we are going to have to offset this leaking methane by taking carbon out of the air and sequestering it in some way.
Sea level rise
This is one area where there is still considerable uncertainty, mainly we because we don’t fully understand how decaying ice sheets behave. The report settles on a conservative range of 50cm to a metre by 2100, but we could reach 50cm by 2050. Taking the lower limit, one of the diabolical results is that the risk of extreme events such as flooding from storm surges, for example, increases disproportionately with sea level rise. Hence a 1 in 100 years event can amplify 1000 times to become a 10 times per annum event. This map shows the implications of a 50cm rise for Australia:
I’ve numbered the images I’ve selected sequentially and given the report’s numbers in brackets.
The ocean is already more acid that it has been for 25 million years, as shown in this graph:
This is important in terms of the evolutionary adaptability of species. In geological time there have been times where ocean acidity has been greater. But changes have also been associated with major extinction events. Current changes are just too fast. This image shows what we can expect in the Great Barrier Reef:
Remember that reefs and shell formation in other species are already being affected. The 2C ‘guardrail’ does not represent safety in terms of ocean acidity.
Changes in our weather
The story here is complex in terms of a climate change imprint and there is plenty of uncertainty about what will unfold. There are some fairly clear general observations, including the fact that the eastern half of the continent has become drier since about 1970 and the western half wetter, with the exception of the SW corner. Here is a record of the inflow to Perth dams:
What chance of returning to the pre-1975 pattern?
There is a very good little section explaining the state of play. This conceptual graph explains beautifully what is likely to happen with temperature rise:
It’s the shaded area under the graph that counts.
The ’emissions budget’ approach
I was delighted to note that the report strongly embraced the ‘climate budget’ approach, which was the basis of my earlier climate crunch post. In fact the report uses the first three graphs I used there. Not so delighted about what it means.
It’s based on the notion that if we want ta 67% chance of staying within the 2C temperature increase guardrail then we must emit no more than 1 trillion tonnes of CO2 equivalent during the first part of this century. Three problems here. First, I don’t like the odds. Given the gravity of what might happen if we go over 2C I’d prefer 99.99% frankly.
Second, I don’t like the 2C guardrail. Ocean acidity is a problem below that level, so is sea level rise, the change of weather patterns and the implications for species extinctions. Moreover, tipping points like the frying of the Amazon and methane release have a fair chance of becoming problematic this side of 2C.
Third, we used up 30% of our budget in the period 2000 to 2008 inclusive.
Furthermore, I’m not convinced that the climate sensitivity assumptions behind the graph fully take account of longer term feedbacks.
Still 2C is a vast improvement on ‘business as usual’ or some half-arsed token effort, as this graph shows:
Sceptics/denialist/contrarions all, please take a good look at where the red splash gets us by 2100. That’s what the best science available is telling us. Once you get to 4-5C you have an ice-free world, and 70 metres of sea level rise eventually. You have a high risk of major releases from all sorts of carbon sinks which would take the temperature even higher. Should it stop at 4-5C you have a a very different planet and the likelihood that civilisation as we know it would not survive. Implied are billions of deaths and a collapse of the human population.
At 5-6C you are looking at habitability only in residual parts of the planet.
Climate crunch is here
To finish, I repeat the initial image in a larger version and what I said earlier:
If we, the world, start to reduce emissions now (impossible) by 3.7% a year, we can get away with an eventual reduction of about 85% by 2050. If we start reducing emissions in 2020 we’ll need to reduce by 9% each year (impossible). If we start in 2015 we can get away with reductions of 5.3% per year (barely possible). But we will have to reach zero net emissions by 2040 and then go negative. Is that possible? Barely, if at all, I suspect.
It’s going to be a near-run thing. Rudd had it right when he said that climate change was the greatest moral challenge of out times. The challenge for Gillard is to seriously take up the challenge. The challenge for Abbott is to avoid being a bit of historical detritus. Best he just get out of the way and be taken out with the tide.
Elsewhere: Climate Progress has a post.
I haven’t attempted to round up local reaction other than a brief comment here.