CO2 Climate Sensitivity Overestimated

CO2 emissions are a primary driver in climate change

A paper in Science published two weeks ago has suggested that climate sensitivity to carbon dioxide emissions is currently overestimated. The one line summary: 'the results imply a lower probability of imminent extreme climatic change than previously thought'. For more exact information read on...

Previous estimates suggest 3K change as the best estimate for doubling CO2 emissions, with 2 - 4.5K as the 66% probability range. The study combined extensive sea and land surface temperatures from the Last Glacial Maximum with climate model simulations; their results estimate a lower median of 2.3 K change in temperature, and reduced the uncertainty range to 1.7 - 2.6K (66% probability).

The uncertainty analysis is still incomplete and work will be done over the coming months to better consider things such as uncertainties in radiative forcings due to ice sheet extent, or different vegetation distributions. From their current estimates however, they seem certain that any climate sensitivities larger than 6 K seem implausible.

At the end of the day, a 2K rise in temperature will still have massive impacts on the natural and built environment, and will contribute to the intensification of the hydrological cycle, making extreme weather events more likely. It is however a gentle reminder that all future climate change scenarios and estimates are estimates and nothing more than that. With time I am certain that these uncertainties will be narrowed down even further. The authors stress that the results do not mean that the threat from human-induced climate change should be treated any less seriously. But seeing as there is very little being done about mitigating CO2 emissions, it means that we have a bit more time than previously thought.

Wind turbine explodes... because of too much wind!

Image Source

You may recall in a very early post of mine that I stated 'more power can be generated in windier conditions' as an advantage of extreme weather events. However, for those who have watched the news in the last 24 hours, it turns out this may not be the case! 

Scotland was hit by a relatively extreme storm yesterday with wind gusts of up to 165mph recorded in the Cairngorms (the highest speeds in 25 years), coupled with localised flooding and heavy snow blasts, even the hardiest of Scots were put to the test (although I do recall one news report yesterday in which the interviewee described it as 'barbecue weather'!)

As of yet "climate models in general do not yield consistent or robust estimates of wind speed changes and the results were very uncertain" according to UK Climate Projections. As a result it is difficult to assign an event such as this to human-induced climate change or whether this is just one of the extremes that occurs naturally under a normal distribution of such event.

There was even an article published a couple of years ago in the Scientific American that climate change would bring about reduced wind speeds. You can find the article here. There is a non-linear trend between wind speed and power generated from a turbine. For example, a 15% increase in wind speed will output 50% more energy. Now for wind farmers across America, this statistic will be alarming, as a small reduce in wind speeds can result in a large loss of power. But as I've just said, their are extremely high levels of uncertainty.

What is certain is that the wind will always blow, but there is likely to be regional winners and losers.

Working Together Saving Tomorrow Today

COP17, Durban, South Africa

Working Together Saving Tomorrow Today - COP17 Slogan

The 17th Conference of the Parties (or COP17) is now well under way (despite a relatively slow start) in Durban, South Africa. Since the UN Convention on Climate Change (UNFCCC) coming into play in 1995, the Conference of the Parties (COP) to the UNFCCC have been meeting annually to assess progress in dealing with climate change.

One of the major arguments to come out of the last 36 hours has been put forward by Health Minister Aaron Motsoaledi, addressing the first Global and Health climate summit (taking place alongside the main COP 17). He has stated that climate change will hurt governments’ "ability to maintain basic health".

The World Health Organisation (WHO) predicts that "changing climate conditions will lead to increases in malaria, cholera and dengue fever, as well as losses of life due to extreme weather events". The message is that health could be one of the first major casualties of climate change. As a result, The summit’s declaration calls on negotiating governments to deliver a binding agreement by 2014 which "places the protection of human health as a primary objective of any agreement". It also calls for a reduction in global greenhouse gas emissions to "avoid a global public health disaster".

However, it is argued that in the long term, the greatest health impacts may not be from acute shocks such as natural disasters, but from gradual build-up of pressure on the natural resources and social system that sustain health, which are already under stress in many parts of the world. It is widely accepted that African countries will be most widely affected by climate change, and therefore high up on the South African health ministers agenda. 

You can keep up to date with all the latest information out of Durban here. The conference ends on the 9th December.

Is Strange Weather in the Air or just On Air?

I came across this clip from NBC news last week which is probably one of the most one-sided reports on climate change causing extreme weather I've seen in recent weeks. It doesn't even try to balance the argument, or even suggest "on the other hand", which is surprising for a major US news network. It devotes a full 2 and a half minutes to suggesting that extreme weather events will become more likely and are a result of climate change. The video concludes by saying "today, no one can deny that extreme weather is here to stay"!

After doing a bit of digging in some journal archives, I came across this interesting paper. It looks at how extreme weather event coverage on US national television has changed over the past 50 years, and assesses whether news coverage can be used almost as a proxy as to whether extreme events are becoming more discernible.

News archives between 1968 and 1996 were used to track records of heat waves, droughts, hurricanes and floods from ABC, CBS and NBC television networks. A control period was used in order to distinguish between 'climate science' and 'global warming' frenzies that hit news and media in the late 80s. Some of the key findings are displayed on the graphs below:

Annual coverage of heat waves on the network news.

Annual coverage of floods on the network news.

Annual coverage of hurricanes on the network news.

The results show a dramatic increase in the coverage of floods and hurricanes since the 1980s, however, it must be noted that the different types of extreme events do not receive equal coverage: for example, annual peaks for droughts contain about twice as many stories as the peaks for heat waves. 

One of the key findings that the data revealed is that surprisingly there is no association between coverage of climate change and the overall coverage of extreme events. They also discovered that whilst total news coverage of extreme events in the US increases dramatically, coverage devoted to extreme events in other countries remains relatively constant (see image below).

Index of extreme weather coverage on the network news by all events and foreign events.

There are a variety of limitations with using a study such as this to show extreme events are linked to anthropogenic change. Media is always subjective and some news stories can be made at the expense of others. Some stories can often dominate the news, whilst others get left behind. Changes in technology, forecasting and the ability to track extreme weather events has also come a long way in the last 50 years and the ability to cover events and show footage will impact whether an event is covered.

Despite not a lot of concrete evidence coming out of reports such as these, it is pleasing that researchers are trying new and innovative ways of collating evidence for climate change.

Incredible Photos of Extreme Weather

I came across this website today which has a collection of some amazing photos of extreme weather events. It is well worth a quick look if you have a couple of minutes spare. They quite literally take your breath away! Here's a couple of my favourites from the site:

IPCC Special Report - Latest Findings on Extreme Weather Events

The report suggests that droughts will intensify during the 21st century

Working Groups I and II for the IPCC have produced a special report for 'Managing the Risks of Extreme Events and Disasters to Advance Climate Change Adaptation' (SREX for short). The findings of the Special Report were presented at the IPCC's 34th session, which is currently being held in Kampala, Uganda. The full report is not available until February 2012, but a 29 page summary has been made available and can be downloaded here.

I've listed some of the key findings below, but I would urge you to take a look at the full report yourselves:

> "A changing climate leads to changes in the frequency, intensity, spatial extent, duration, and timing of extreme weather and climate events, and can result in unprecedented extreme weather and climate events."

> There is evidence that some extremes have changed as a result of anthropogenic influences, including increases in atmospheric concentrations of greenhouse gases. It is likely that anthropogenic influences have led to warming of extreme daily minimum and maximum temperatures on the global scale.

> "It is likely that the frequency of heavy precipitation or the proportion of total rainfall from heavy falls will increase in the 21st century over many areas of the globe."

> "Average tropical cyclone maximum wind speed is likely to increase, although increases may not occur in all ocean basins. It is likely that the global frequency of tropical cyclones will either decrease or remain essentially unchanged."

> "There is medium confidence that droughts will intensify in the 21st century in some seasons and areas, due to reduced precipitation and/or increased evapotranspiration."

> There is high confidence that changes in heat waves, glacial retreat and/or permafrost degradation will affect high mountain phenomena such as slope instabilities, movements of mass, and glacial lake outburst floods.

The summary is very cautious with it's findings and confidence levels, stating that "Extreme events are rare, which means there are few data available to make assessments regarding changes in their frequency or intensity." As has been discussed in previous posts and seen in the current academic literature, it becomes very difficult to isolate a single event, like a heatwave or a heavy rainstorm, and say that event was caused by the human element of climate change.

Despite this, the report is yet another contribution to the scientific community suggesting that anthropogenic impacts are having a direct impact on extreme weather events.

Extreme Winters Caused by natural Solar Cycle?

Living not far outside of London growing up, the idea of a thick blanket of snow to play in on a winter's day was only ever a distant fantasy. You see it in the American movies all the time, and you soon learn that a 'white Christmas' doesn't really exist. When the snow fell in 2009, my inner child only had one thing in mind!

What's the significance of this? Well, it was the coldest winter on record in over 25 years, and the UK received record levels of snow. It would be easy to throw climate change to an extreme anomalous event such as this, but recent findings suggest an alternative...

Climate scientists at the UK Met Office have recently carried out a new study on the fluctuations of the sun's UV radiation. They attempted to create a link between solar activity and seasonal weather.

Satellite measurements were used and fluctuations in solar radiation were discovered to be five times as large as previously thought. They put their data into the Hadley Centre model and were able to show how these fluctuations affected regional weather.

The paper emphasises that there findings do not suggest a link to long-term global warming, rather that there is a real correlation between ultraviolet levels and meteorological variables. They show that there is actually little direct change in globally averaged temperatures as the solar activity drives cold winters in northern Europe and the United States, but mild winters are subsequently found over southern Europe and Canada.

How does it work?

UV is absorbed in the stratosphere (the upper atmosphere) by ozone. When there is less UV to absorb, the stratosphere is relatively cooler. The Hadley centre model shows that the effects of this percolate down through the atmosphere. It is described in the paper as a 'top-down stratosphere to troposphere pathway'. As it does this, it changes wind speeds, including the jet stream that circles the globe above Europe, Russia and North America. The resultant change is a reduced air flow from the west to the east, moving colder air into the UK and northern Europe. The image below shows these changes in wind speed and pressure between Ocotber and March 2010. There is then a re-distribution of temperatures across the region, leading to the milder winters in southern Europe and Canada.

Source

Is it quite as clear cut?

The scientists suggest that other factors may have been at play for the colder winter temperatures, including the decline of sea ice levels and El Nino. In all honesty, it could be any combination of these factors, but they suggest that the solar cycle was acting in a way to facilitate these conditions.

What's the advantages of this (other than building giant snowmen)? 

The UV measurements could be used for better forecasting. UV levels won't be able to tell us what the day-to-day weather will do, but it would enable improved forecasts for winter conditions months ahead. They would play an important role in long-term contingency planning.

In summary, the winter weather seen across the UK and Atlantic between 2009-2011 appears to back up the scientists findings. The next stage of investigation would be to look at UV measurements across a longer time-scale, to see if the patterns hold true.