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Showing posts with label IPCC. Show all posts
Showing posts with label IPCC. Show all posts

Thursday 23 April 2015

It's time to 'Do the math' again

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By David Spratt

Have we gone mad? A new report released today explains why contemporary climate change policy-making should be characterised as increasingly delusional.

As the deadline approaches for submissions to the Australian government's climate targets process, there is a flurry of submissions and reports from advocacy groups and the Climate Change Authority.

Most of these reports are based on the twin propositions that two degrees Celsius (2°C) of global warming is an appropriate policy target, and that there is a significant carbon budget and an amount of "burnable carbon" for this target, and hence a scientifically-based escalating ladder of emission-reduction targets stretching to mid-century and beyond.

A survey of the relevant scientific literature by David Spratt, "Recount: It's time to 'Do the math' again", published today by Breakthrough concludes that the evidence does not support either of these propositions.

The catastrophic and irreversible consequences of 2°C of warming demand a strong risk-management approach, with a low rate of failure. We should not take risks with the climate that we would not take with civil infrastructure.

There is no carbon budget available if 2°C is considered a cap or upper boundary as per the Copenhagen Accord, rather than a hit-or-miss target which can be significantly exceeded; or if a low risk of exceeding 2°C is required; or if positive feedbacks such as permafrost and other carbon store losses are taken into account.

Effective policy making can only be based on recognising that climate change is already dangerous, and we have no carbon budget left to divide up. Big tipping-point events irreversible on human time scales such as in West Antarctica and large-scale positive feedbacks are already occurring at less than 1°C of warming. It is clear that 2°C of climate warming is not a safe cap.

In reality, 2°C is the boundary between dangerous and very dangerous climate change and 1°C warmer than human civilisation has ever experienced.

In the lead up to the forthcoming Paris talks, policy makers through their willful neglect of the evidence are in effect normalising a 2.5–3°C global warming target.

This evidence in "Recount: It's time to 'Do the math' again" demonstrates that action is necessary at a faster pace than most policy makers conceive is possible.



Related

- It's time to 'Do the math' again
http://www.climatecodered.org/2015/04/its-time-to-do-math-again.html

- RECOUNT - It's time to 'Do the math' again
http://media.wix.com/ugd/148cb0_938b5512abfa4d4e965ec8cc292893f7.pdf

- Two degrees of warming closer than you may think
http://arctic-news.blogspot.com/2015/02/two-degrees-of-warming-closer-than-you-may-think.html

- The real budgetary emergency and the myth of "burnable carbon"
http://arctic-news.blogspot.com/2014/05/the-real-budgetary-emergency-and-the-myth-of-burnable-carbon.html

It's time to 'Do the math' again | by David Spratt http://arctic-news.blogspot.com/2015/04/its-time-to-do-math-again.html

Posted by Sam Carana on Thursday, April 23, 2015

Sunday 23 November 2014

IPCC too conservative?

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Earlier this month, the Intergovernmental Panel on Climate Change (IPCC) released its 5th Assessment Report (AR5), stating that: "Surface temperature is projected to rise over the 21st century under all assessed emission scenarios. It is very likely that heat waves will occur more often and last longer, and that extreme precipitation events will become more intense and frequent in many regions. The ocean will continue to warm and acidify, and global mean sea level to rise. Many aspects of climate change and associated impacts will continue for centuries, even if anthropogenic emissions of greenhouse gases are stopped. The risks of abrupt or irreversible changes increase as the magnitude of the warming increases."

That does sound scary. So, what would happen if the IPCC's projections are too conservative? Could humans, together with many other species, go extinct within the next few decades? What are the risks that this could eventuate? Below follows an assessment using graphics by Sam Carana.


1. Ocean Heat

Below is what the IPCC says:


Below is a graph produced by Sam Carana, based on NOAA data. For more background, see this earlier post.



2. Sea level Rise

The image below shows what the IPCC says.


If ocean heat will continues to rise as pictured in the image by Sam Carana, then thermal expansion alone will cause more sea level rise than foreseen by the IPCC. Furthermore, extensive melting on Antarctica and Greenland can result in additional sea level rise. Below is a sea level rise graph produced by Sam Carana, based on NASA/GSFCs data, as discussed in this earlier post.



3. Arctic Sea Ice

The image below shows what the IPCC says.


If ocean heat will continues to rise as pictured in the image by Sam Carana, then Arctic sea ice will disappear much earlier than anticipated by the IPCC. An exponential trendline based on sea ice volume observations shows that sea ice looks set to disappear in 2019, while disappearance in 2015 is within the margins of a 5% confidence interval, reflecting natural variability.


A linear trend would be inappropriate, given the growing impact of feedbacks that can each be expected to reinforce sea ice decline, while there can also be interaction between these feedbacks, further accelerating sea ice decline. Albedo change is one such feedback, but there are numerous other ones, such as storms that have more chance to grow stronger as the area with open water increases.

In conclusion, an exponential trendline is more appropriate than a linear trendline, as also illustrated by above comparison, which shows that a linear trendline has 9 years fall outside its 95% confidence ionterval, versus 4 years for an exponential trendline. as discussed at the FAQ page.

Rapid decline of the snow and ice cover on the Northern Hemisphere is furthermore supported by rapidly rising surface temperatures over the Arctic, as well as greater intensity of heatwaves. Below is what the IPCC says on this.


Before further discussing surface temperatures, let's look into one of the feedbacks that could hugely increase temperatures, methane.


4. Methane

 The IPCC appears to underestimate of the amount of methane that is contained in sediments under the Arctic Ocean and prone to be released as temperatures rise, as discussed in this earlier post and in this earlier post.

The image below, based on data from the IPCC and the World Metereological Organization (WMO), with an added observation from a NOAA MetOp satellite image, illustrates the recent rise of methane levels and the threat that methane levels will continue to rise rapidly.

When looked at from a longer range of years, above image fits in the black square on the image below.

As ocean heat keeps increasing and warming in the Arctic keeps accelerating due to feedbacks such as Arctic sea ice decline, huge methane eruptions from the seafloor of the Arctic Ocean threaten to push up methane levels even further. The image below shows exponential rise based on data of East Siberian Arctic Shelf (ESAS) releases alone, as discussed in an earlier post.


Non-linear rise is supported by the fact that methane's lifetime increases as more methane enters the atmosphere.

5. Surface Temperatures

The IPCC expects that, worst case, global average temperature could rise by 13 degrees Celsius by 2300, as illustrated by the image below.


The situation could be much worse than foreseen by the IPCC, due to the non-linear way feedbacks can hugely increase temperature rises.




The threat is that such rapid temperature rises will appear at first in hotspots over the Arctic and eventually around the globe, while also resulting in huge temperature swings that could result in depletion of supply of food and fresh water, as further illustrated by the above image, from an earlier post, and the image below, from another earlier post.

The situation is dire and calls for comprehensive and effective action, as discussed at the Climate Plan blog.




Post by Sam Carana.
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