Predicting Extreme Heat

WHO: Brigitte Mueller and Sonia I. Seneviratne (Institute for Atmospheric and Climate Science, Eidgenössiche Technische Hochschule (ETH) Zurich, Switzerland)

WHAT:  Seeing if you can predict extreme heat from a lack of moisture in the ground.

WHEN: July 16 2012

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

TITLE: Hot days induced by precipitation deficits at the global scale (subs required)

Using data correlations to try and predict extreme heat – useful for drought and disaster planning

I’m sure many of you rush out each week to get the newest copy of the Proceedings of the National Academy of Sciences when it hits the stands (yeah, I don’t either) but this paper came to my attention as something a bit interesting.

The researchers were hoping that there might be a relationship between how dry the soil is in the lead up to heatwaves and the extreme heat that follows. If extreme heat can be better predicted, then it’s easier for local or state governments and emergency services to prepare for it.

To measure lack of rain, they used the Standardised Precipitation Index (SPI) which is a measure of drought that only looks at rainfall (so doesn’t count water supply levels, water demand or runoff losses). The index works on a number system where -2 is exceptionally dry, zero is normal amounts of rain, and +2 is exceptionally damp. This paper looked at soil moisture across the globe, but as an example, here’s the SPI map for the USA this May/June when they started their severe heatwave in several parts of the country.

The paper found that there is a relationship, where lack of surface moisture is generally followed by extreme heat a few weeks later. Keep in mind though, the favourite saying of statistics people around the world: correlation does not mean causation. So while there may be a connection between dry soil and coming heatwaves, that doesn’t mean that dry soil causes heat waves of course.

Interestingly, the researchers found that the relationship between lack of surface moisture and extreme heat was asymmetrical – the correlation was stronger for really extreme heat and weaker for average heat. Which is good because it means this method can help predict the really horrendously hot days better than the averagely uncomfortable hot days.

Predicting the days when it’s so hot even the Koalas will ask for a drink (Velovotee, Flickr)

The data used was SPI data for 3, 6 and 9-months between 1979-2010, and a ‘hot day’ was defined as a temperature that was warmer than 90% of all the other days. The strongest correlation between lack of soil moisture and extreme heat was found in North and South America, Europe, Australia and China. This means that in those areas, localised research could be done to look at how to best predict the potential for extreme heat before it occurs, which will allow for emergency services to prepare for things like more hospitalisations from heat stroke or bushfire conditions, and give local governments time to make public service announcements to try and stay indoors and hydrated, etc.

What’s this got to do with climate change? Well, currently for the North American summer of 2012, the heat records are beating the cold temperature records by 10 -1. This is what climate scientists are talking about when they say carbon pollution is loading the dice for more extremes – normally there should be one record high for every record low. So if extreme heat is going to become more common in some places as we experience greater levels of climate change from continuing carbon pollution being poured into the atmosphere, being able to plan for it is a really good idea.

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Increased CO2 at the Bottom of the Food Chain – Phytoplankton

WHO: Kunshan Gao, Guang Gao, Yahe Li, Bangqin Huang, LeiWang, Ying Zheng, Peng Jin, Xiaoni Cai, Wei Li, Kai Xu, Nana Liu (State Key Laboratory of Marine Environmental Science, Xiamen University, China)
Juntian Xu (School of Marine Science and Technology, Huaihai Institute of Technology, Lianyungang, China)
David A. Hutchins (Marine Environmental Biology, Department of Biological Sciences, University of Southern California, Los Angeles, California)
Donat-Peter Häder (experimental design and data analysis, Möhrendorf, Germany)
Ulf Riebesell (Helmholtz Centre for Ocean Research Kiel (GEOMAR), Kiel, Germany)

WHAT: Large project in the South China Sea to work out the effects of increased CO2 on important algae

WHEN: July 2012

WHERE: Nature Climate Change, Vol 2 Issue 7 2012

TITLE: Rising CO2 and increased light exposure synergistically reduce marine primary productivity (sub required)

The bottom of the food chain contains the unsexy and somewhat unpopular plants and animals. Let’s face it, most of us are not going to get as worked up over algae as a really cute polar bear. But climate change is going to affect the algae too, so this large project between the State Key Laboratory of Marine Environmental Science in China, the University of Southern California and a centre for ocean research in Germany set out to find out what increased CO2 levels mean for phytoplankton.

Phytoplankton – not as cute as polar bears (Logical Progressions, Flickr)

Phytoplankton are microscopic plankton that we can only see when there’s too many of them and they create an algal bloom. They are part of a larger group of algae, which are the building blocks of the food chain in the ocean and undergo photosynthesis (just like plants do) to create 40% of the primary production (really basic organic compounds) in the ocean.

So while they may not be the coolest things in the ocean, they’re pretty important.

Oceans absorb a really large amount of the carbon pollution we’re currently putting into the atmosphere – around 1millon tonnes of CO2 every hour is absorbed and a quarter of that gets removed from the atmosphere and stored in the ocean. The increasing amount of carbon pollution we’re creating means more and more CO2 is getting absorbed by the ocean, making the ocean more acidic.

Phytoplankton algal bloom in the Ross Sea, Antarctica (NASA Goddard Photo and Video, Flickr)

Acidic oceans are not fun for the local residents. Acid makes shells thinner and reduces the defences of animals that have them, and it bleaches coral, turning the coral white. So, if we ignore the need to reduce carbon pollution and allow 800 – 1000 parts per million (ppm) of CO2 to collect in the atmosphere by 2100, what’s that going to do to the ocean and the algae?

That much atmospheric CO2 will increase ocean acidification by 100- 150% (depending on how much we pollute and interactions with other bio-systems), which is really going to suck if you’re a shell-wearing animal or you hide in coral. It’s also going to affect the ability of phytoplankton to grow and therefore produce the basic organic compounds the ocean needs.

The researchers did controlled lab tests with different levels of CO2 concentrations in sea water (between 390ppm which is what the world is currently at and 1000ppm) and different strengths of sunlight. They then checked these against the experiments conducted in the ocean to make sure their results were realistic.

To a certain point, the increased sunlight and CO2 helps the phytoplankton grow, but beyond that point, the phytoplankton start getting stressed, and in extreme situations even start emitting carbon at night after absorbing it during the day.

Apart from the fact that humanity is really in trouble at the point where the ocean starts releasing carbon rather than storing it for us, an ocean where the building block organisms are stressed isn’t going to be very productive for growing things or living.

Higher CO2 can reduce the ability of phytoplankton to grow by up to 81% depending on how much you stress them, but the more CO2 is present, the less sunlight it takes to stress the phytoplankton and reduce their growth. The decrease in phytoplankton also saw an increase in Haptophytes, which form toxic algal blooms.

The effects of CO2 on the phytoplankton can be kept neutral, but only if the amount of sunlight is kept under 30%, which is impossible outside of a lab. The researchers were not able to work out how these effects on phytoplankton would relate to CO2 absorption and sequestration in the ocean, or food production for the rest of the food chain. However, in a world where we allow 800- 1000ppm of CO2 into the atmosphere, there’s unlikely to be any humans around either, since beyond around 450ppm irreversible positive feedbacks kick in and make our planet seriously non-linear (unpredictable and extreme).

So obviously for our sakes and for the poor phytoplankton too, we should reduce our carbon emissions and not let that happen.

Sea Level Rise and the Effects of Carbon Pollution Reduction

WHO: Michiel Schaeffer (Environmental Systems Analysis Group, Wageningen      University, The Netherlands),
William Hare (Potsdam Institute for Climate Impact Research, Potsdam, Germany),
Stefan Rahmstorf (Potsdam Institute for Climate Impact Research, Potsdam, Germany),
Martin Vermeer (Geoinformatics, Aalto University School of Engineering, Finland)

WHAT: Estimates of sea level rise with different levels of CO2 emission reduction

WHEN: 24 June, 2012

WHERE: Nature Climate Change, Vol 2 Issue 7 2012

TITLE: Long-term sea-level rise implied by 1.5 °C and 2 °C warming levels

One of the consequences of climate change is going to be sea level rise as the globe slowly warms and ice sheets and glaciers continue to melt.

The issue is trying to predict exactly how much sea level is going to rise by and how much we can do about it. This paper was published in June in the journal Nature Climate Change, which is an offshoot of the journal Nature, one of the most highly respected peer reviewed scientific journals in the world.

The researchers used several different scenarios for looking at how sea levels rise with rising temperatures and used what’s called a semi-empirical model to predict the numbers out to 2100 and 2300.

A semi-empirical model is one that combines observed and recorded data (thermometers, tide records) with paleo data (ice cores, fossil records). Since there is only recorded tide gauge data from the previous 130 years, this is not a large enough sample to use for long range predictions. It would be like using one week of training to determine whether I could run a marathon. So the researchers combined the historical data with the recorded data and calibrated to test how realistic the combination was.

Calibrating is where you test something for a single result several times and work out what your error margin is. For example, you could measure three different bottles of Coca Cola you bought at the store, and one might have 600mL, one might have 603mL and the third might have 598mL. They’re all supposed to be 600mL, but since most things have a margin of error, not all are exact.

Same thing for science experiments. The researchers calibrated their data for the years 1000 through to 2006 and found that their results were similar to other scientists who had done similar experiments.

Several scenarios were used; two with no reductions in carbon emissions (from the Copenhagen Accord agreement), two where the earth stays within 2C of warming (one that looks at all polluting gasses – carbon, ozone and sulphur based and one that looks at the delay of emission reductions until 2100), and one where the earth stays within 1.5C of warming (with early carbon emission reductions keeping pollution under 400 parts per million (ppm) in the atmosphere).

Three of the scenarios (delaying until 2100 and two in between) used data that will be included in the IPCC 5th Assessment Report which is the newest data on climate change. The finalised 5th report won’t be published by the UN until the end of 2014.

One of the scenarios for 2C (the one with the different polluting gasses) was developed by an international scientific group and published in Climactic Change. The scenario for 1.5C was developed by a group working for the International Energy Agency and published in the journal Energy. Another hypothetical scenario where global carbon emissions are zero by 2016 was also used to see what effect historical emissions might have on sea levels.

So what did they find? Already, the data for the 20th Century (1900-1999) has higher sea levels than any time in the past 1,000 years.

Using the scenario from the Copenhagen Accord (the equivalent of doing nothing) a sea level rise of 72 – 139cm by 2100 was predicted.

Even with zero emissions by 2016 there’s a predicted sea level rise of 40 – 80cm by 2100. The reason for this is because climate systems are inert. Which means they can absorb a lot of change before you can see it and that there’s a time lag between putting the pollution into the atmosphere and seeing the consequences.

Sea level rise precitions (MERGE400 = 1.5C, Stab2 and RCP3-PD = 2C, CPH = no action, others are variations in between). Dark lines are the median (middle) predictions, shaded areas show the uncertainty range.

So what does this mean in reality for climate change and people? It means that even if we limit carbon pollution in the atmosphere to 400ppm the conservative estimate is for a 54cm rise in sea level, which is knee-deep on me. And if 400ppm doesn’t sound like a very big number, just remember the US EPA recommends that more than .002ppm of mercury in your drinking water is dangerous. You don’t need large amounts of compounds for them to be dangerous to your (or the planet’s) health.

The good news is the research shows that even though there’s uncertainty regarding non-linear (unpredicted) changes in ice sheet melt, and we’re going to experience sea level rise continuing over the next 50 years from pollution already in the atmosphere, emissions reductions do show less sea level rise than the ‘do nothing’ or ‘delay’ scenarios.

So while we are going to have around half a metre of sea level rise in the next 50-100 years (I’d hold off on purchasing that beachfront property), with strong emission reductions, the sea level might peak sometime before 2100 and hopefully head back towards normal.

Why the huge range of numbers and years? Firstly because the researchers can’t say what and how much the world is going to do about climate change in the next few decades, and secondly because you can’t be absolutely (as in 100%) certain that anything is going to happen until it actually does. But the data gives us a pretty clear indication that the year 2100 will see somewhere between .5 – 1m of sea level rise.

Hello world!

Welcome to my wordpress home for Read the Science. Please bear with me while I work out all the nuances of a new platform (for me).

What I hope to do with this site is to post my translation of current climate science each week. In conversations with people who are less of a science nerd than I am, I’ve discovered a gap between what the science and scientists are saying and what the public is hearing. So I’m trying to bring a new take on current peer-reviewed published papers.

Recommendations of papers I haven’t seen or that you think should be blogged about are welcome. I will be focusing on climate change, but will occasionally take the time to deviate to different research that I find either interesting or relevant.

I hope you find it interesting and relevant as well!

Happy reading,
Amy

Renewable Hybrid Systems: Optimising Power Grids

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WHO: Robert Huva, Roger Dargaville and Simon Caine

WHAT: Electrical power grids powered by renewable energy

WHEN: Published in Energy [41 (2012) 326-334]. April 2012

WHERE:  Earth Sciences department, The University of Melbourne, Melbourne, Australia

TITLE:  Prototype large-scale renewable energy system optimisation for Victoria, Australia (subs required)

One of the major barriers to the full scale take-up of renewable energy to power electricity grids has been the need to provide baseload power to users. This is the power required to keep your fridge running through the night, the power to keep traffic lights running all day and night and many other things. It’s the minimum amount of electricity required to keep the modern world running.

Renewable power is not constant, because the sun doesn’t shine at night and it’s not always windy, and water runs through rivers at different speeds depending on the time of year. So in order to provide the constant power needed, a hybrid system of renewable energy sources needs to be used.

This paper from the University of Melbourne in Australia has done that. They used detailed weather maps for the state of Victoria to determine the best locations for solar and wind power.

Victoria, Australia (Google maps)

Best locations for wind (blue) and solar (red)

They then combined the outputs of the solar and the wind with other forms of renewable energy, including hydro-electricity (running water spinning a turbine to make power) and wind-hydro hybrids where excess wind power will pump water up a hill to a raised dam, and when the wind dies down, the dam gets opened and the hydro starts producing electricity.

They found that the entire electricity needs of the state of Victoria could be met from renewable power sources with only 2% back up from natural gas needed.

 Hybrid renewable systems – meeting demand

So what does this mean for reducing the effects of climate change?

It means that renewable power is viable in the state of Victoria, which will allow the state to switch from it’s current power source of brown coal (which is much dirtier than your standard black coal when it burns, releasing more carbon pollution into the atmosphere).

Making the transition to a hybrid renewable system will also significantly reduce carbon emissions in the state of Victoria since 49% of energy in the state comes from coal power. It will create a large number of new jobs, as the renewable energy market increases from 12% (in 2011) to the 98% that has been shown in the research, which we will need to do in the next 30 years if we want to avoid catastrophic climate change.

How can it be done? By ensuring areas are able to access either localised power production (in rural or remote areas), or smart grids (in cities) that are able to monitor and respond to changing power production levels and changing energy use levels, hybrid systems of renewable electricity are fully capable of providing the power we need to run our lives.

*Full disclosure: The name is not a coincidence – this research was conducted by my brother as part of his PhD research (yes, I’m using my brother’s research to test out my own blog 🙂 )