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The Conversation: Most Australians believe that climate change is real and want to learn more about it, but the debate in the media and on the internet makes it difficult for lay people to know who and what to believe. There are uncertainties in climate science, as in any scientific field, and scientists are quite open about these. But they are often misrepresented.
In the claims and counterclaims by various climate change experts and other commentators, one yardstick that can be used is whether the “science” being put forward has passed the scrutiny of peer-review before being published. Peer review is a process in which relevant experts assess the competence, significance and originality of the research.
There are a number of recent assessments of peer-reviewed climate change science:
- The Intergovernmental Panel on Climate Change (2007): Climate Change 2007 Synthesis Report
- The Royal Society (2010): Climate Change: A Summary of the Science
- The Australian Academy of Science (2010): The Science of Climate Change: Questions and Answers
- The Climate Change Commission (2011): The Critical Decade.
Within each of these reports there is a distinction between science that is robust and science that is relatively uncertain. Chapter 6 of the IPCC (2007) Synthesis Report lists 21 robust findings and 18 key uncertainties. These are grouped and summarised below.
Robust findings: the things we know
- There is clear evidence for global warming and sea level rise.
- Changes that are being observed in many physical and biological systems are consistent with warming.
- Due to the uptake of anthropogenic CO₂ since 1750, ocean acidity has increased.
- Most of the global average warming over the past 50 years is very likely due to anthropogenic greenhouse gas increases.
- Global greenhouse gas emissions will continue to grow over the next few decades, leading to further climate change.
- Due to the time scales associated with climate processes and feedbacks, anthropogenic warming and sea level rise would continue for centuries even if greenhouse gas emissions were to be reduced sufficiently for atmospheric concentrations to stabilise.
- Increased frequencies and intensities of some extreme weather events are very likely.
- Systems and sectors at greatest risk are ecosystems, low-lying coasts, water resources in some regions, tropical agriculture, and health in areas with low adaptive capacity.
- The regions at greatest risk are the Arctic, Africa, small islands and Asian and African mega-deltas. Within other regions (even regions with high incomes) some people, areas and activities can be particularly at risk,
- Some adaptation is underway, but more extensive adaptation is required to reduce vulnerability to climate change.
- Unmitigated climate change would, in the long term, be likely to exceed the capacity of natural, managed and human systems to adapt.
- Many impacts can be reduced, delayed or avoided by mitigation (net emission reductions). Mitigation efforts and investments over the next two to three decades will have a large impact on opportunities to achieve lower greenhouse gas stabilisation levels.
Key uncertainties: the things we’re not sure about
- Observed climate data coverage remains limited in some regions.
- Analysing and monitoring changes in extreme events is more difficult than for climatic averages because longer data sets with finer spatial and temporal resolutions are required.
- Effects of climate changes on human and some natural systems are difficult to detect due to adaptation and non-climatic influences.
- Difficulties remain in reliably attributing observed temperature changes to natural or human causes at smaller than continental scales.
- Models differ in their estimates of the strength of different feedbacks in the climate system, particularly cloud feedbacks, oceanic heat uptake and carbon cycle feedbacks.
- Confidence in projections is higher for some variables (such as temperature) than for others (such as precipitation), and it is higher for larger spatial scales and longer averaging periods.
- Direct and indirect aerosol impacts on the magnitude of the temperature response, on clouds and on precipitation remain uncertain.
- Future changes in the Greenland and Antarctic ice sheet mass are a major source of uncertainty that could increase sea level rise projections.
- Impact assessment is hampered by uncertainties surrounding regional projections of climate change, particularly precipitation.
- Understanding of low-probability/high-impact events and the cumulative impacts of sequences of smaller events is generally limited.
- Barriers, limits and costs of adaptation are not fully understood.
- Estimates of mitigation costs and potentials depend on uncertain assumptions about future socio-economic growth, technological change and consumption patterns.
Do we know the world is warming due to human activity?
The IPCC statement most often challenged by so-called sceptics is “Most of the global average warming over the past 50 years is very likely due to anthropogenic greenhouse gas increases”. Those who are keen to dig deeper into the peer-reviewed literature on this issue can read more:
- Chapter 9 of the IPCC (2007) Working Group 1 report
- Easterling and Wehner (2009) Is the climate warming or cooling?
- Stott et al (2010) Understanding and attributing climate change
- Kaufmann et al (2011) Reconciling anthropogenic climate change with observed temperature 1998–2008.
Some of the other common issues raised about climate change science have been addressed by CSIRO.
Navigating the maze of information about climate change science is challenging for a layperson. Recent assessments of the peer-reviewed literature put this into perspective. There are many robust findings about the science, and these provide a basis for action through mitigation of greenhouse gases as well as adaptation to reduce our vulnerability to climate change impacts.
While there are also scientific uncertainties that need further research, these don’t undermine a compelling scientific case for increased risk management.
Author: Kevin Hennessy , Principal Research Scientist, Marine & Atmospheric Research at CSIRO
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“Most of the global average warming over the past 50 years is very likely due to anthropogenic greenhouse gas increases.”
“Very likely”? then you say this:- “•Global greenhouse gas emissions will continue to grow over the next few decades, leading to further climate change”.
Shouldn’t you say “Global greenhouse gas emissions will continue to grow over the next few decades, very likely leading to further climate change”.
The IPCC uses the words “very likely” because they have no proof, but you just suddenly state that it is a fact!
Now isn’t that somewhat alarmist, or do you have some proof that no one else knows about?
And where have you analysed the economic cost to us all of following the IPCC’s CO2 emission reduction demands?
Don’t you think that your whole blog reeks of alarmism with very few facts and consequences?
Cheers
Roger
http://www.rogerfromnewzealand.wordpress.com
Roger,
We suppose that you are addressing to the author of this post, as we reproduced it for the reading of people like you which sometime don’t access many web pages at a time. As you will read Kevin Hennessy (author of this post) is a scientist at CSIRO and all details have been mentioned their. You may like to write to Kevin by going through the source.
Best
Dear Roger,
I understand that you are a denialist. I have noticed that somewhere else you demanded empirical proof of Global Warming in a manner as if you are inviting someone in a ‘duel’.
While your disagreement to any view expressed here is also another view, I think you are barking up a wrong tree.
This, IMO, is not a science forum. This is a forum of people who look at the world’s worsening conditions in a certain way. If you have a constructive narrative that can better explain and help the concerns of the people of Himalayas, why not write a complete post and send it to the publishers?
Thanks guys for your replies.
First of all I have to say that I believe it is only ethical to post on YOUR site in this public forum, information that is consistent and verifiable- regardless of which author you employ or use.
Pabitra,
Yes I do often demand empirical proof for the unproven “Anthropogenic CO2 causes Global Warming” and although I do not intend it as a duel, I believe, considering the seriousness of the economic consequences of following the IPCC’s demands for CO2 emission reductions, it is absolutely necessary that a definitive scientific proof be published for all to see. A proof that explains all the disproving factors, of the above mentioned hypothesis, that are readily found and are currently unaddressed as well as having empirical proof of the CO2 – atmospheric warming mechanism. For your information, there appears to be no such paper.
I hear your point about this blog not being a science forum but you must be aware that you are printing quasi scientific literature as if they are the truth.
Although I realise that things may well be tough for the people of the Himalayas, to expound your opinions in this fake authoritarian way, in order to alter their beliefs will not help these good people in the least.
I notice that you have labeled me as a “Sceptic” by which label you imply that I am somewhat strange and therefore of no account, but without scepticism we have Alarmism which unlike scepticism, does not enhance the truth but propogates the very opposite.
I suggest that the publisher of this blog take a deep look at his concience.
Cheers
Roger
http://www.rogerfromnewzealand.wordpress.com
Dear Roger,
I do not label you as anything, except that you seem to deny AGW part of Climate Change. I think this forum publishes anything that has connection to the Climatic realities of the mountains – it has lots of science, some ‘voodoo science’ and social, economic, public health and administrative policy related issues ‘as told’ by a commenter. It appears to me that you prefer material distilled from a science lab through peer reviewed publications. I am not sure if Climate Himalaya is exactly that.
I would like to assure you that, as far as people of the Himalayas are concerned, both side of the story are open and I also strongly hope they will choose the one right for their future. When it is a matter of survival a debate about empirical proof for a scientifically established point seems moot to me – particularly when such properly established scientific facts have not held the Himalayan people in any good stead for centuries. The economic deprivation, neglect, destruction and backwardness of the place is heart wrenching to say the least.