Monthly Archives: October 2012

Too Hot in Texas

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New modelling of climate change effects on mosquito populations in the United States has surprising results – it might get too hot in summer even for the mosquitoes

WHO: R A Erickson, S M Presley, Department of Environmental Toxicology, and Institute of Environmental and Human Health, Texas Tech University, Lubbock, Texas
K Hayhoe, Department of Political Science, Texas Tech University, Lubbock, Texas
L J S Allen, Institute of Environmental and Human Health, and Department of Mathematics and Statistics, Texas Tech University, Lubbock, Texas
K R Long, Department of Mathematics and Statistics, Texas Tech University, Lubbock, Texas
S B Cox, Department of Environmental Toxicology, and Institute of Environmental and Human Health, Texas Tech University, Lubbock, Texas and Research and Testing Laboratory, LLC, Lubbock, Texas

WHAT: Population modelling for the Asian Tiger mosquito which carries dengue fever under two climate change scenarios

WHEN: 5 July 2012

WHERE: Environmental Research Letters, Vol. 7, No. 3 (July-Sept 2012)

TITLE: Potential impacts of climate change on the ecology of dengue and its mosquito vector the Asian tiger mosquito (Aedes albopictus)

This group of researchers in Texas decided it would be interesting to look at different climate change emissions scenarios from the IPCC and see what the effect of climate change might be on everybody’s ‘friend’ the Asian Tiger mosquito. For those of you who haven’t met the Asian Tiger mosquito, it is the type that carries dengue fever, which makes you very sick. So understandably, how climate change affects the population spread of this mosquito is pretty important.

The Asian Tiger mosquito is not your friend (Wikipedia)

The researchers looked at three localised areas in the US to run their model – Lubbock TX (where their University is), Atlanta GA, and to look at the potential geographical spread of the mosquito; Chicago IL.

Many of the predicted consequences of climate change are currently happening decades ahead of schedule, and one of the consequences is the expansion of the tropical belt by around 2- 4.8o latitude since 1979. This wasn’t expected to occur until 2100, so it means mosquitoes could be moving north faster than previously predicted.

The climate scenarios used were the A1FI (high emissions) and B1 (medium emissions) from the IPCC Special Report on Emissions Scenarios, which relate to approximately 970ppm (A1FI) and 550ppm (B1) of CO2 in the atmosphere. To give some context for those numbers, we’re currently sitting at 391ppm. 550ppm is where feedback loops have already kicked in and there are large ocean ‘dead zones’ where there’s not enough oxygen for plant and animal life. 970ppm is the IPCC’s ‘worst case scenario’ where there is mass biodiversity loss and a high likelihood of mass extinction events.

IPCC Emissions Scenarios A1FI (above) and B1 (below)

Anyway, back to mosquitoes. The researchers used three of the world’s best and most detailed climate models; the CM3 model from the UK’s Hadley Centre, the National Centre for Atmospheric Research model in Colorado, and the National Oceanic and Atmospheric Administration’s CM2.1 model. They used the mean temperature data from their three locations and combined it with the climate model to work out what the average temperatures might look like under the scenarios. Then they applied those conditions to mosquito populations to see what might change.

What they found was very interesting, and not what the researchers had originally expected. While the population size and duration of the mosquito season in Chicago increased across the board along with the potential dengue fever outbreak size, in Lubbock and Atlanta the mid-summer temperatures got too hot even for the mosquitoes.

Chicago (left) and Lubbock (right) with mid and end of century predictions. Chicago has an increase in mosquito population while Lubbock has a noticeable mid-summer die-off of mosquitoes (from paper)

While the mosquito season in Lubbock started earlier and had a potential for greater dengue fever outbreaks, the super-hot summer temperatures under both of the climate change scenarios modelled led to mosquitoes dying and a reduction in potential dengue fever outbreaks. This could have many social and health policy ramifications in the areas studied and also shows that the local level effects of climate change may manifest in ways we haven’t previously thought of.

Humans are notoriously difficult to predict and we don’t know yet what humanity will do about climate change in the near future. This gets combined with natural systems and feedbacks that are highly integrated and complex which means one seemingly unrelated process may be triggered in another previously unrelated process.

However, complexity doesn’t mean that models aren’t relevant or useful and the proverbial baby should be thrown out with the bathwater. Models give us a range of possibilities to plan for and allow humans the opportunity to act in our own long term best interests.

Currently, we’re not acting for our long term well being, and humanity is currently burning carbon at a rate that matches or beats the A1FI high emissions scenario that very probably leads to mass extinction, including humans. Which means that now would be the time to stop burning fossil fuels. Before Texas becomes so scorching hot that even the mosquitoes die from the mid-summer heat.

The Forests of Planet Ocean

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Estuaries are the forests of the ocean and they take up carbon 90 times more efficiently than land forests

WHO: Colin Campbell (Science Advisor, Sierra Club BC, PhD Marsupial Evolution, UC Berkley)

WHAT: ‘Blue Carbon’ report looking at how carbon is stored in oceans

WHEN: August 2010

WHERE: Sierra Club BC – in print and online

TITLE: Blue Carbon British Columbia: The Case for the Conservation and Enhancement of Estuarine Processes and Sediments in B.C.

Since I’ve moved to Canada, I’ve learnt a lot about salmon and it’s a pretty tough gig from what I can tell. Everyone wants to eat you along the way (including humans like me – yum!) and evolution decided it would be a good idea to swim up the river – way to make it harder!

Salmon – it’s a hard knock life (photo: Dan Bennett, flickr)

But even harder again – once baby salmon have hatched and are swimming back down the river to eat and grow and become edible for me, they have to also make the switch into salt water which is impressive in any animal.

Changing from fresh water to salt water as a fish takes a whole heap of osmoregulation, which is the transfer of water into and out of your cells to keep an even salt balance on both sides of the cell membrane. When there’s too much salt on one side, the water moves to dilute it, which is the reason we feel dehydrated after eating a lot of salty food. So a salmon changing to salt water would be like you or I changing to only drinking salt water instead of fresh water. Salmon can do this, we would not survive.

How do salmon do this? Well it involves estuaries. Estuaries are the underwater grasslands at river mouths which look pretty gross to walk through in your bare feet when you’re going swimming. But if you’re a salmon, it’s your training ground. Salmon will hang out in estuaries full of eelgrass or salt marshes for a week or two until their bodies switch to salt water. The area is full of microbes dissolved in the water for the salmon to eat and the eelgrass provides a great hiding place for salmon that aren’t yet fast enough to swim away from everyone who wants to eat it. Without estuaries, the salmon race down the river and shoot straight out into the salt water, which is quite a shock to their systems.

Eelgrass – salmon training ground and underwater forest (photo: Eric Heupel, flickr)

This paper from the Sierra Club here in British Columbia talks about estuaries other feature – they’re great carbon sinks, and we need more of them. Carbon moves around our planet in a cycle with sources and sinks. Humans burning fossil fuels are a huge source of it and the sinks can’t keep up the balance (hence ocean acidification and global warming). So the more carbon sinks we can preserve and create the better for our survival.

Because eelgrass, mangroves and salt marshes are in the shallow water, they get lots of sunlight, which allows them to photosynthesise. 1km2 of mangroves can store the same amount of carbon as 50km2 of tropical rainforest and estuaries are constantly sucking carbon dioxide in, and releasing oxygen while pushing carbon further down into the sediment on the ocean floor.

They suck carbon in, send oxygen out and provide a training ground for animals – so far there’s no downside.Except that many estuaries have been or are being reduced by human development. In the Fraser River here in Vancouver alone, 99% of the delta marshlands are gone due to flood prevention dyking, farmland or development. That’s a whole lot of carbon that could be sucked into the estuary that isn’t.

Currently, it’s estimated that BC estuaries sequester 180,200 tonnes of carbon per year, even with their diminished size due to humans. When you realise that Metro Vancouver’s carbon emissions were 10.5 million tonnes in 2010, estuaries take up 1.7% of our emissions each year. If we keep burning carbon, we will need a lot more estuaries. Additional benefit for our own self interest as well of course is that more estuaries means bigger salmon runs and more delicious food for us, the bears, the seals, the whales, the eagles and all the rest.

As Vancouver aims for its 2020 Greenest City targets, one of the most efficient ways of sequestering more carbon while also reducing our emissions might not be our forests, but our underwater forests – the tidal estuaries.

How Does Your Wind Farm Grow?

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Calculating what the global saturation point for wind energy would be and if we can generate enough wind power to power half the globe.

WHO: Mark Z. Jacobson (Department of Civil and Environmental Engineering, Stanford University, Stanford, CA)
Cristina L. Archer (College of Earth, Ocean, and Environment, University of Delaware, Newark, DE)

WHAT: Predicting the effectiveness of scaling up wind power to provide half the world’s power requirements by 2030.

WHEN:  September 25 2012 PNAS, Vol 109, No. 39

WHERE: Proceedings of the National Academy of Sciences of the United States of America

TITLE: Saturation wind power potential and its implications for wind energy

I learnt about a new law today; Betz’s Law. Betz was a guy who decided to calculate exactly how much energy could be extracted from the wind by a turbine at any given time mathematically (as you do). He worked out that no turbine can take any more than 59.3% of the energy from the wind. To be able to conceptualise this, you have to think about wind like a physicist. The first law of thermodynamics states that you can’t create or destroy energy; you can only convert it to different forms. Therefore, all wind is just energy in a certain form, and in any system there is a point where the transformation is most efficient and beyond there it takes a lot of effort to get any more energy from the system.

There’s a really cool project being done in the US, where a website has taken data from the National Digital Forecast Database and created a visual representation of what wind would look like if you could see it move. It’s strikingly beautiful, and looks a lot like a Van Gogh painting.

Wind Map by Fernanda Viegas and Martin Wattenberg of hint.fm

The question this paper looks at is: since there is a limit to the amount of energy you can take from a turbine, what is the maximum wind power that can be extracted from a geographical area? They called it the ‘Saturation Wind Power Potential’.

They came up with some interesting findings, as well as probably having a lot of fun along the way because they used 3D Models to do it (I’m telling you, my chemistry molecular model kit was much more like playing with Lego than actual ‘science’). They got into the detail and calculated the potential wind power at 10m off the ground, 100m off the ground (the standard height of a wind turbine) and 10km off the ground in the jet stream.

They then looked at whether it would be possible to scale up wind power globally to meet 50% of the world’s power needs by 2030. Actually measuring the wind power potential for more than 1 Terrawatt (TW) of energy is not possible as there isn’t enough wind power installed yet. But they did mathematically work out that we would need 4million 5 Megawatt (MW) turbines to supply half of the world’s electricity needs in 2030 (5.75TW).

They did four simulations with different turbine densities, because how close together wind turbines are affects their ability to produce power. Put them too close together and they start stealing their neighbour’s wind power. Overall, up to 715TW, the increased number of turbines increases the amount of power in a linear straight line. Once you get above that it slows down and flattens out – once again you need to put much more effort in to get power out.

Predicted wind power saturation potential (from paper)
Grey line – global wind power potential, black line – wind power potential on land only

The saturation point, where no matter how many more turbines you add, they’ll just be stealing energy from each other and not adding anything to the total, was 2,870TW of power globally. Interestingly, they found the wind power available in the jet stream (10km above the ground) was 150% greater than the wind power available 100m above the ground.

There were also some big changes to the results depending on the density. If we placed 4million 5MW turbines and packed them in at 11.3 Watts per m2 (W/m2), they would be too close together and the collected power wouldn’t match the target for half the world’s power by 2030. If you spread them out to 5.6W/m2 the output is still too low. However, once you’ve got them spaced at 2.9W/m2, they produce enough power to meet the required demand.

4million turbines meet demand when they’re 2.9W/m2 apart or further (from paper)

So it turns out wind turbines don’t like it when you cramp their style. But, you can pack them in a bit tighter, only if you then have enough space between your wind farm and your neighbour’s wind farm. It’s a bit like playing wind farm Tetris.

What does this mean though? It means that we can ramp up world wind power production to levels that will meet half our power needs in 2030, which can be integrated with hydro, solar and other renewables with smart grids to power our cities and lifestyles without burning fossil fuels. But it also means we need to think about where we are putting wind farms and how much space they need to be as efficient as possible. We need that renewable energy, so we can’t cramp the wind turbines’ style!

Improved Drought Prediction: Now With Six Soil Layers

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Predicting the severity of drought using multiple indices

WHO: Liu Sun, Scott W. Mitchell (Department of Geography and Environmental Studies, Geomatics and Landscape Ecology Research Laboratory, Carleton University, Ottawa, Ontario, Canada)
Andrew Davidson (Department of Geography and Environmental Studies, Carleton University, Ottawa National Land and Water Information Service, Agriculture and Agri-Food Canada, Ottawa, Ontario)

WHAT: Improving the accuracy of drought prediction in the Canadian prairies

WHEN: September 2012

WHERE: International Journal of Climatology, Vol 32, Issue 11, September 2012

TITLE: Multiple drought indices for agricultural drought risk assessment on the Canadian prairies (subs req)

Are you tired of your drought prediction methods using only two layers of soil structure to track moisture? Sick of having to work with constants when you’d much rather be using dynamically calculated values? Well, this paper is for you.

Drought is going to be a big issue with climate change as rainfall patterns change and move. Agricultural yields are not able to increase as quickly as the world’s population increases but people still need to eat.

Drought is going to affect all of us as extreme weather increases from climate change, whether it’s through increased food prices (I’m still upset about bacon), local water restrictions (stop hosing down concrete – stop it now), local ecosystems being stressed or climate refugees from newly arid areas. This is one of the great ironies about climate change – you can’t negotiate with or spin physics. The laws of physics aren’t going to change because of some slick advertising campaign trying to prop up a floundering status-quo, and climate change isn’t going to avoid you if you ignore it.

In terms of drought modelling and prediction, each method currently used has slightly different ways of predicting drought, which means they can’t easily be compared. The method the researchers used for this paper was to modify the original Palmer Drought Severity Index to include more variable data. They accounted for six soil layers and a new evaporation calculation. Instead of using constant numbers for the characteristics of the climate, they allowed each of those to be calculated too. This means most people end up with a giant math headache from extra calculations, but by allowing for greater variability, they also allowed for greater sensitivity and accuracy in their model. The new model was also tested for accuracy against the Palmer Drought Severity Index, Standardised Precipitation Data and Palmer Moisture Anomaly Index methods.

For any of these models to work, they need approximately 30 years of monthly weather data (temperature, rain etc). This paper looked at 1976 – 2003 as it was the period of most consistent data in the area they were studying (the Canadian Prairies).

Then they got into the serious math using all kinds of things like a ‘thin plate smooth spline surface fitting method’ to remove the noise from the data and a linear regression to remove yield differences from better agricultural practices, allowing them to just look at the data that was climate affected.

The different models: red dot indicating the new model. Spot on for most, slightly under for some (from paper)

It went pretty well; their predictions were more accurate than the other standard drought prediction methods, except for predicting extreme drought, which their model under-predicted. This is possibly because there wasn’t a lot of data points in the previous 30 years with extreme drought, so as extreme weather becomes more normal under climate change, their model will probably get more accurate. They also found that the model is more accurate for arid locations, as flooding messes up the model.

As the extreme, unpredictable realities of climate change start to affect everyone in the next decade or so, this drought prediction model will likely be very useful. Predicting the extremes as best we can is going to become an essential tool for preventing massive crop failures as well as loss of human lives.

Predicting the Unpredictable: Tropical Hydrology

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Unpredictable tropical storms from climate change and changing land-use patterns are going to mess with water cycles

WHO:  Ellen Wohl (Department of Geosciences, Colorado State University, Fort Collins, Colorado)
Ana Barros (Duke University, Pratt School of Engineering, Durham, North Carolina)
Nathaniel Brunsell (Department of Geography, University of Kansas, Lawrence, Kansas)
Nick A. Chappell (Lancaster Environment Centre, Lancaster University, Lancaster, UK)
Michael Coe (Woods Hole Research Center, Falmouth, Massachusetts )
Thomas Giambelluca (Department of Geography, University of Hawaii at Manoa, Honolulu, Hawaii )
Steven Goldsmith (Department of Geography and the Environment, Villanova University, Villanova, Pennsylvania)
Russell Harmon (Environmental Sciences Division, ARL Army Research Office, North Carolina)
Jan M. H. Hendrick (New Mexico Institute of Mining and Technology, Socorro, New Mexico)
James Juvik (Department of Geography and Environmental Studies, University of Hawaii-Hilo, Hilo, Hawaii)
Jeffrey McDonnell (Department of Forest Engineering, Resources, and Management, Oregon State University, Corvallis, Oregon)
Fred Ogden (Department of Civil and Architectural Engineering, University of Wyoming, Laramie, Wyoming)

WHAT: Looking at what we know about tropical water patterns and working out what we don’t know

WHEN: September 2012

WHERE: Nature Climate Change, Vol 2 Issue 9, September 2012

TITLE:  The hydrology of the humid tropics (subs. req)

This paper from Nature Climate Change does two things; it looks at what we know about tropical water cycles (hydrology) and also the gaps in our knowledge (scientists- always wanting to know more!).

So what do we know?

Firstly, let’s define the ‘tropics’. This paper looks specifically at the humid tropics which is anywhere that precipitation exceeds evaporation 270 days a year or more, and is generally 25⁰ latitude either side of the equator.

The tropics highlighted in red (Wikipedia)

Fun fact – the tropics is where the term ‘the doldrums’ comes from. It’s officially known as the ‘Intertropical Convergence Zone’ and is the area where the winds coming from the northern hemisphere and the southern hemisphere collide, creating erratic weather patterns and violent thunderstorms. This poses a few issues in the face of climate change. Climate change will make weather more extreme and the effects will be non-linear, so this means the tropics are about to get even less easy to predict.

There are many areas of the tropics where land-use changes are affecting water cycles. Deforested areas outnumber the remaining forest, which is already having a measurable effect on rain patterns in Brazil; extending the dry season and rain being more intense when it does occur. It’s estimated that deforestation in the South Eastern Amazon has increased the flow of water to the ocean by 20% in the last 40 years. These changes and others will likely be amplified with increased climate change effects.

Billions of people rely on the major rivers in the tropics for their fresh water, and flows of water, energy and carbon are all closely linked to the amount and age of vegetation in the area. Changes in water flows and rain patterns can be disastrous, and can occur from combinations of land-use change, deforestation and climate change. So messing with the systems can create large changes. The closely linked relationship between vegetation type and water cycles also means that my idea of trying to grow an Australian gum tree here in Vancouver when I feel homesick is a bad one.

However, while water cycles are being modified across the tropics by land-use changes, deforestation and climate change, the effects are going to vary region by region, making predictions difficult. There are far fewer weather measuring stations in tropical areas than temperate areas, so less data overall. The researchers identified moisture cycling, water catchment processes and long term data collection as areas that need improvement if we are going to be able to accurately predict global warming changes in the tropics.

Number of weather stations in temperate vs tropical areas (from paper)

In order to answer important questions that relate to the availability of fresh water for billions of people and extreme weather in areas that have earthquake activity as well as cyclones there needs to be a detailed body of data. Forewarned is forearmed, especially if systems are heading towards possible tipping points, and this paper would like researchers to study more tropical areas to better understand them.