AGW: Can we cut it?
As expectations steadily decrease that any sort of broad-reaching international climate deal will come out of the 17th Conference of Parties in Durban at the end of this month, the message from a recent spate of research is becoming increasingly urgent: we need to do a lot more, and a lot faster, if we want to have any sort of chance at limiting global warming to 2°C above pre-industrial levels, and thus avoid some of the more damaging impacts of human-induced climate change.
Last week we had the International Energy Agency warning that under a "new policies" scenario, the world would only get one third down the track to where it wants to be towards this goal. This week, the journal Nature Climate Change has published research by an international team of scientists, led by the University of Exeter, highlighting the fact that the task of limiting warming to 2ºC is becoming increasingly daunting, with a warning that we will only achieve the target of limiting it to safe levels if CO2 emissions begin to fall within the next two decades and eventually decrease to zero.
And while the emphasis is on how quickly emissions need to drop in the next few decades, one of the report's more surprising findings, says lead author Professor Pierre Friedlingstein, was how few options are available to us to achieve this. The research exploring the potential efficacy of differing mitigation responses in meeting the target of limiting warming to 2°C shows that links between near-term decisions, long-term behaviour and climate-sensitivity uncertainties constrain mitigation options.
"We know we need to tackle global warming, but our research really emphasises the urgency of the situation," said Friedlingstein. "The only way for us to achieve a safe future climate will be to reduce emissions by at least 3 per cent, starting as soon as possible. The longer we leave it, the harder it will be."
Prof Friedlingstein and his colleagues at Exeter used a climate model to explore how soon, how quickly, and by how much future carbon dioxide emissions must be reduced to determine whether the internationally agreed goal of limiting global temperature rise to 2°C can be met.
The researchers found that that if the sensitivity of the climate system to carbon dioxide was approximately as expected, the target could only be attained if medium to high emission-reduction rates began within the next 20 years and net emissions eventually fell to zero or became negative. If climate sensitivity was high, then the target would become even less attainable.
In a worst-case scenario of high climate sensitivity, the team found that the world would need to work towards negative emissions if we were to have a chance to keeping temperatures within the 2°C target. This, of course, would mean using largely unproven carbon capture and storage technology, combined with aggressive mitigation rates starting in the coming decade.
The best-case scenario of low climate sensitivity allows longer delays and more conservative mitigation rates, but still requires emissions to be eventually cut by at least 90 per cent.
The report also shows that if the world delayed reducing global emissions by just 10 or 20 years, then we would need to make much steeper reductions in order to meet a 2°C warming target.
Comments on this article
Trevor trust the scientists
Trevor, water vapour concentration is a positive feedback from CO2 concentration and not vice versa because:
Water vapour has a far quicker cycle in the atmosphere, days maybe weeks for most of the water molecules, carbon is recycled over almost geological time scales.
So the CO2 is always there exerting its greenhouse influence while water vapour changes wildly over time in any one place, but the extra average heat over large areas caused by CO2 means there is higher water vapour on average.
Also we're not dumping huge amounts of water vapour into the atmosphere, we're dumping CO2 (and other greenhouse gases).
Think about it like the water cycle is the wheel of the bike, while the CO2 cycle is the gear attached to the pedals.
Plants are limited in their ability to take up CO2 because there are only so many of them, and when CO2 is abundant, they rapidly run into other limiting factors such as lack of light, water, space or nutrients. Most plants are water stressed, not CO2 stressed.
If you look at the year by year CO2 concentration graphs, you can see the earth's plants breathing, because there is a difference in vegetation cover between North and South hemispheres so the CO2 goes through an annual oscillation, but every year the oscillation ends higher than it started the previous year.
A pause in warming?
We have not experienced a pause in warming. It continues, as you would expect as we steadily increase one of its drivers, the concentration of CO2.
Trevor hopes we can cut it out.
Trevor, the carbon dioxide does accumulate. At the rate of gigatonnes per year. That is why there is concern.
Some will dissolve in the ocean, some will be absorbed by plants if we allow extra vegetation to grow, but most will stay in the atmosphere.
The accumulation in the ocean is believed to be deleterious and we are actually reducing the vegetation. No joy there.
To actually reduce the CO2 in the air, something will have to change.
I don't think any of this is controversial any more.
The controversial bit is what will change and who will pay? These are the real and substantial issues. Some think let it rip, market forces will decide. Some think that the issue requires government intervention.
Thanks David Arthur BUT.......................................
David ,
Thanks for your comments BUT...........please explain this :
How can a trace-atmospheric-gas at 0.039 % ( CO2 ) control a gas which can be between 1 % & 4 % of the atmosphere at any time depending on where you measure it ??
Nature is being "anthropomorphised" by your description about recycling. Plants don't care where the CO2 comes from...they just absorb & metabolise it( with 'solar power' ),create sugars & starches & excrete O2 & CO2 without compunction !
There is no such thing as "ecological balance". It is a figment of a computer-operator's imagination. It was hypothesised as a means of explaining the environment in a mechanical sense as human beings attempted to simplify, understand & explain the random processes around them of which they are a part .
It has no reality.
There is a CO2 cycle but it is highly variable & is NOT FIXED to exclude additional input as you suggest.Whatever can be utilised is utilised,sometimes there is an excess & sometimes a shortage.At night (when photosynthesis is not occurring) plants absorb O2 & give-off CO2. For this reason ,many plants grown in hot-houses have high levels of CO2 supplied to them during the day & the hot-houses are 'vented' at night.These levels can vary from 1,000 ppm ( 0.1%) up to 10,000 ppm ( 1%) depending on plant requirements & response.
I respect your ardour but I think you are succumbing to AGW propaganda. Try a little research on some of your basic tenets & you may find the clarity with which you hoped to imbue me.
Regards , Trevor.
ATTENTION TREVOR RIDGWAY
Trevor has made some good points, except that his logical foundation is completely and utterly wrong.
Trevor writes: "Water vapour is the principle 'greenhouse gas' & is the planet's temperature control mechanism , not CO2, ..."
FYI, Trevor, while it is true that water vapour is the principle greenhouse gas, atmospheric water vapour content is determined by atmospheric CO2 content.
Trevor continues: "... the level of which has been shown to be an effect of rising temperature and not a cause."
FYI, Trevor, there are feedback mechanisms between temperature and NATURAL (ie non-anthropogenic) CO2 transfer between atmosphere and carbon stores such as oceans, permafrost, wetlands and soil. This feedback mechanism is a large part of Pleistocene climate dynamics, for example.
However, anthropogenic recycling of geosequestered carbon (ie burning fossil fuels) to the atmosphere is a large, non-natural perturbation of the climate system. As such it is NOT one of these natural feedback processes.
I hope this helps clarify the issue for you.
AGW : Can we cut it ?
Can we cut it out ! Gosh ! I hope so !
I am fed up with articles like this one Sophie.
You may write out of conviction but it is all emotive clap-trap , not a shred of scientific detail . Just about as informative as one sports commentator interviewing another sports commentator about his opinion of the stock market !
Keith Williams : Higher temperature ( e.g. Summer ) means that water absorbs heat & evaporates providing a cooling effect which produces more water vapour in the atmosphere which equals more clouds , therefore more heat transfer to the upper atmosphere by condensing to water & then to ice giving off latent heat , more ice crystals reflecting heat ( or absorbing it & melting & becoming rain....but nevertheless , transferring heat to the top of about 80 % of the atmosphere where the photons can easily escape through the rarified air , only about 20 % of the atmosphere is above the clouds , back out into space from whence they came , mostly from the Sun ).
Water vapour is the principle 'greenhouse gas' & is the planet's temperature control mechanism , not CO2, the level of which has been shown to be an effect of rising temperature and not a cause.
The CO2 "we" produce is not chemically different to all the other CO2 & can be utilised by living organisms ( plants & plankton ) and merely becomes a part of an extensive Carbon-Cycle .It is well within this cycle to absorb & utilise & there is a huge variability in this quantity being recycled.
It doesn't accumulate.
Garbage in=garbage out
More carbon dioxide IN means more heat retained and OUT come all the consequent (and inconvenient) effects!!
Seems reasonable to be alert and try some modelling and data collection to me-but i,m not a rabid denier!!
Leading the way
Chris
Australia is not going to be reducing it's emissions by 5% - we are going to be buying indulgences from around the world to make it appear as though we are !
Leading the way
well good old Australia is leading by the front and we're going to reduce our output by 5% by 2020.
Yeah well that should have a big effect on the " if the world delayed reducing global emissions by just 10 or 20 years"
Oh yeah, and then one day it's going to be zero emmissions. What a load of crap.
Distorting the truth
Keith,
Empirical data show that deaths and death rates from extreme weather and climatic extremes have declined over the past few decades.
http://reason.org/files/deaths_from_extreme_weather_1900_2010.pdf
Put simply the IPCC does not explicitly blame Climate Change:
“Long-term trends in economic disaster losses adjusted for wealth and population increases have not been attributed to climate change, but a role for climate change has not been excluded (medium evidence, high agreement).”
As we have experienced a pause in warming for the last 10 years and scientists like Dr Ben Santer have asked:
In order to separate human-caused global warming from the “noise” of purely natural climate fluctuations, temperature records must be at least 17 years long, according to climate scientists.
Let's wait until 2015 to confirm the trend, actually you may not have a choice on this one :-)
Real World?
Scientists do not make ambit claims ( salary negotiations excepted?). So, when attempting predictions of climate extremes (note not climate averages) which are especially difficult, they qualify such predictions with even greater uncertainties. Live with it guys, even when precise data from the historical record is put in (not garbage) there is some uncertainty in the expected average change which is magnified when predicting extremes. Any honest attempt at reporting this, not to mention developing policies for rational governments, businesses or individuals should be clear about the uncertainty.
Shoot the messenger by all means, but it is a fact that carbon dioxide converts solar radiation to heat more effectively than the major constituents of air. We are putting significant quantities out there which will insure greater heating until it is removed. That is not opinion, it is known. The question is what, if anything, to do about it. This article makes the point that, if we want to make a given measurable difference, the cost will be greater later on. That is independent of whether the response is left to governments or to market forces.
Distorting the draft IPCC report
Timothy,
Trying to obfuscate by distorting the IPCC draft report is a classic denialist tactic. It deserves to be highlighted.
Sophie Vorrath's article and the draft IPCC report makes very clear that "urgent" is a reasonable word to describe action needed to combat climate change.
Put simply, higher temperatures means more moisture in the atmosphere and more intense flooding in some parts & more droughts in others. The financial and human costs of extreme weather all around the world in 2011 bear this out.
Sitting on our hands and watching things get worse is not a reasonable approach to this problem, which has been foreshadowed for decades by the experts.
Extreme misinterpretation is more of a distraction.
@ Timothy Norcott: Clearly, selecting one sentence from a report, taking it out of context and misinterpreting it, is cluster of disingenuity.
The IPCC report is very clear about the risks of extreme weather.
AGW
That is not a translation. It is a willfully misinterpretation of the necessary qualification that all predictions are subject to uncertainty. It is possible that the magnitude of temperature increases is being underestimated. So a genuine skeptic might be concerned about that, but no, the skeptic is dogmatic that the projections are overestimates, or preferably, that they can be ignored. Bury your heads, but be careful, the sand may be hot!
Distraction
This is just a distraction from the latest leaked IPCC draft report which states:
“Uncertainty in the sign of projected changes in climate extremes over the coming two to three decades is relatively large because climate change signals are expected to be relatively small compared to natural climate variability”.
Translated: The natural climate forces are stronger than we thought, and we give up, we can’t say whether it will get warmer or colder in the next twenty years.
Get into the Real World
Here we go again ... more scaremongering using shamefully inadequate (for making predictions) computer models. Just another example of the old computer adage: garbage in means garbage out.