Understandable Earth Science

I’ve noticed that there seems to be a lot of anti-CCS views being aired on Twitter at the moment, along with some CCS news articles that are factually incorrect (see bottom of this post).

So here is a quick overview of what CCS is and isn’t. I intend to write more detailed blogs discussing these points sometime soon – just need to find the time.

So, what is CCS?

  • CCS stands for carbon capture and storage
  • CO₂ is captured from energy production and industry. That CO₂ would otherwise end up in the atmosphere and cause global warming.
  • The captured CO₂ is permanently* stored deep (2-3 km) underground in pore spaces in the rock.
  • CCS is the only feasible way of reducing CO₂ emissions from industry – especially the steel industry, necessary for building wind turbines!
  • CCS is a way to reduce CO₂ emissions while we are transitioning from a fossil-fuel to low-carbon energy infrastructure.
  • CCS is a fully developed and tested technology.
  • CCS is a potential way of getting negative CO₂ emissions – i.e. reducing CO₂ in the atmosphere by combining CCS with burning of biofuels for energy.
  • Implementing CCS is cheaper than dealing with the consequences of global warming.

* CO₂ will be stored deep in rocks on the timescale of thousands to millions of years. So technically not “permanently” on a geological timescale, but permanent on a human timescale and easily long enough to buffer global warming.

Now to address some of the misconceptions about CCS.

What CCS is NOT:

  • CCS is NOT an excuse to keep burning fossil fuels indefinitely.
    • CCS can minimise CO₂ emissions while we transition from a fossil-fuel to a low-carbon energy infrastructure over the next 50-100 years. I do not know anybody working with CCS that thinks it is a long term solution that will let us keep burning fossil fuels.
  • CCS is NOT unnecessary for reducing our CO₂ emissions.
    • Many reports (including IPCC) show CCS is needed to meet climate targets.
    • Existing energy infrastructure cannot yet cope with the intermittency of many forms of renewable energy.
    • CCS is currently the only way to reduce industry CO₂ emissions.
  • CCS is NOT storing CO₂ in caves / fractures.
    • In the vast majority of storage sites, CO₂ is and will be stored in rock pore spaces many kilometres underground. Up to 20% of the volume of a rock can be empty space – think of a box of marbles and the gaps between the marbles. That is where the CO₂ will sit. And the storage rocks are deep, with many impermeably layers on top of them which means the CO₂ will not leak out of the ground.
  • CCS is NOT a new, un-tested technology.
    • Lots of CCS pilot-projects exist that show CO₂ can be captured at large scale from power plants, and the world’s first CCS power station –Boundary Dam – was opened in Canada last year (2014).
    • The storage technology behind CCS has been used for years in the oil industry for something called enhanced oil recovery (EOR) where CO₂ is pumped into an oil field to get more oil out of the ground, and there are lots of storage pilot projects that show that the CO₂ can be injected into deep rocks, without causing earthquakes and without leaking.

What CCS is and is not

So, onto the newspapers that are getting their facts wrong.

On January 6th 2015, The Guardian published this article, including the following paragraph:

“CCS is strongly supported by energy companies like Shell. It involves the sequestration and piping of carbon dioxide into underground fissures and currently aids fossil fuel extraction, as well as allowing their continued burning long into the 21st century.”

Carbon dioxide is NOT pumped into underground fissures! It is injected into pore space in rocks!

Then we have this pleasantly optimistic article in the Irish Times published on January 8th 2015 that contains 2 slip-ups I feel need correcting.

Firstly is this paragraph with similar problems to the Guardian article:

 “Statoil has been trying out CCS at its Sleipner natural gas field in the North Sea since 1996. Since then, it has injected some 14 million tons of carbon dioxide into geological caverns and “successfully” proved that it is technically feasible, the company’s Olav Skalmerås said in Bonn.”

There are no caverns in the Sleipner natural gas field. The CO₂ stored in Sleipner (and the natural gas that has been stored in the rocks at Sleipner for thousands to millions of years) exists in the pore spaces between grains in the rock. For more information, see this article by the British Geological Survey.

Next was this paragraph:

“Novel approaches to carbon capture are also being tested. One €8.75 million project in Iceland called CarbFix, which has EU support, involves capturing carbon dioxide from a power station, dissolving it in water and effectively “mineralising” it as basalt for injection into volcanic fields.”

This is a different kind of technology from most CCS storage projects; here the CO₂ is stored by reacting it to make a solid mineral. Maybe I am nit-picking, but “effectively “mineralising” it as a basalt” is incorrect. Basalt is not a mineral – it is a rock (a volcanic rock that forms from lava flows, like the current Bárðabunga / Holohraun / Nornahraun eruption). In this project, basalt is the storage rock that the CO₂ is being injected into. The CO₂ reacts with calcium in the basalt to produce a carbonate mineral called calcite, which should be stable for thousands to millions of years. For more information, see the CarbFix website.


In my first climate-related blog I talked about why I was so angry that the world wasn’t taking action to prevent climate change – 10 years ago the wedges concept, introduced  by Pacala and Socolow [1], gave a clear prediction of how our annual CO₂ emissions were increasing and identified ways to reduce emissions. Back then, the world was still thinking in terms of how CO₂ *emission rates* affect climate change. Since then we have realised that emission rates are relatively unimportant and that global cumulative CO₂ emissions are what we need to keep an eye on.

This is because CO₂ has a long residence time in the atmosphere – if we were to completely stop burning fossil fuels and emitting CO₂ today, it would take up to 35 thousand years for all of the CO₂ we emitted since the industrial revolution to be re-absorbed [2] (if you want to know more about that, there is a nice blog here). This means that our CO₂ emissions over decades, even centuries, are pretty much instantaneous on the carbon-cycle timescale.

CO₂ residence

Figure 1: Carbon is stored as fossil fuels for millions of years. When we take it out of the ground and burn it, we are releasing CO₂ instantaneously on geological timescales. It then takes tens of thousands of years for that CO₂ to be removed from the atmosphere and be stored long-term in the Earth.

The amount of global warming will be controlled by the amount of CO₂ hanging around in the atmosphere, and, because it hangs around in the atmosphere for so long, that is controlled by the total amount of CO₂ we have emitted, rather than how fast we are emitting it. In 2009, Allen et al [3] calculated the Earth will warm by ~2 °C for every 3.67 trillion tonnes of CO2 that we emit [4]. If we want a good chance of avoiding global temperature rise of more than 2 °C, the most CO2 we can emit is 3.67 trillion tonnes – total! period! ever!.

Reducing emission rates just delays the 2 °C temperature rise – it doesn’t prevent it. Stabilising emission rates buys us time but doesn’t solve the problem. The only way to solve the problem is to completely stop emitting CO₂.

This next diagram, simplified  from the IPCC 2014 report (Figure SPM.5, p9 [5]), is a nice illustration of  how much we can expect the global temperature to rise because of the total amount of CO₂ we emit. The x-axis shows cumulative CO₂ emissions since 1870 in gigatonnes of CO₂. (GtCO₂) The y-axis shows the temperature increase compared to pre-industrial temperatures. There are different ways of modelling the climate response to carbon dioxide emissions, and that is why this graph is plotted as a grey band, rather than a single line – the band represents the range of expected global warming according to lots of different models and calculations. Those different models and calculations all agree pretty well.

Expected warming from CO₂ emissions

Figure 2. Global warming due to total CO₂ emissions with observed data and future predictions for different mitigation strategies

According the graph, when we have emitted 3670 Gt CO₂ (3.67 trillion tonnes), we can expect the global temperature to have risen between ~1.4 and ~3.1 °C (black dotted line shows 3.67 trillion tonnes vs 2 ܄C).

The black ellipse labelled “Observed” plots our actual total CO₂ emissions between 1870 and 2005 against the observed warming (as an average of the years 2000 to 2009 compared to an average of the years 1861 to 1880). As you can see, it fits the predicted warming very well.

The red line shows the cumulative total CO₂ emitted as of today [4], December 23rd 2014 (2150 Gt CO₂) and that, no matter what happens, we are already committed to global warming of between 0.8 and 1.8 °C.

The other ellipses are predictions for the amount of CO₂ we will have emitted in the year 2100 for different CO₂ mitigation strategies, and the amount of global warming we would expect. Figure 3, below, is simplified from Figure SPM5 of the IPCC 2014 report and shows the corresponding CO₂ emission scenarios. The blue scenario (blue ellipse in Figure 2, blue band in Figure 3) represents the likely outcome if we use an aggressive strategy to cut CO₂ emissions and are actually able to completely stop emitting CO₂ and start creating negative emissions – actively taking CO₂ out of the atmosphere faster than nature. The yellow scenario represents a CO₂ reduction strategy that sees us managing to stabilise global CO₂ emission rates at their current levels (i.e. the emission rate doesn’t increase) and then decrease emission rates in about 30 years time. In this scenario, we would still be releasing around 50 Gt CO₂ every year, to start with, and that means we would have spent our CO₂ budget within about 30 years; by 2100 we would have emitted 4-5 trillion tonnes of CO₂ and would see global warming of 2.5 to 3 °C. The orange scenario shows what would happen if we slow the increase in emission rate and stabilise CO₂ emissions in about 3 years time – by 2100 we would have emitted ~ 6 trillion tonnes of CO₂ and would see global temperature rises of 3 – 4 °C. The red scenario represents “business as usual” – what we would expect to happen if we didn’t make any special effort to reduce CO₂ emissions. In this scenario, emission rates would continue to increase over time and we are looking at > 6.5 trillion tonnes of CO₂ emitted with temperature rises of > 4 °C by the year 2100.

Predicted CO₂ emissions

Figure 3: Predicted annual CO₂ emissions over time for different mitigation strategies

In summary, if we want a good chance at avoiding a 2 °C global temperature rise, then we can’t emit more than 3.67 trillion tonnes of CO₂. We have already emitted more than half of that in just the last 145 years. Our global CO₂ emission rates are continuing to rise and if we don’t take action quickly, we will have reached that limit within 30 years.

Notes and references:

[1]  Pacala, S. & Socolow, R. Stabilization Wedges: Solving the Climate Problem for the Next 50 Years with Current Technologies. Science 305, 968–972 (2004).

[2]  Archer, D. Fate of fossil fuel CO₂ in geologic time. Journal of Geophysical Research 110, (2005)

[3] Allen, M. R. et al. Warming caused by cumulative carbon emissions towards the trillionth tonne. Nature 458, 1163–1166 (2009).

[4] Reference [3] talks about “the trillionth tonne” – why are you talking about a budget of 3.67 trillion tonnes?

CO₂ emissions can be described in terms of mass of CO₂, or mass of C (i.e. the mass of carbon in carbon dioxide): The element carbon has an atomic mass of 12 and oxygen has an atomic mass of 16. So carbon dioxide has a molecular mass of 44, which is 3.67 times greater than the mass of carbon. Allen’s paper [3] and the website http://trillionthtonne.org/ both discuss CO₂ emissions in terms of mass of carbon – emitting 1 trillion tonnes of carbon (as carbon dioxide) will produce 2 °C warming. To convert this to mass of CO₂ we just multiply by 3.67. The graphs I used in this blog post used emissions and emission rates for CO₂ rather than just C, so I used CO₂ emissions and emission rates to make things simpler. The 2150 Gt CO₂ I quoted as having been released between 1870 and today was calculated by looking up the real-time cumulative total C-emissions from http://trillionthtonne.org/ (586 Gt) and multiplying it by 3.67.

[5] http://ipcc.ch/pdf/assessment-report/ar5/syr/SYR_AR5_LONGERREPORT.pdf

A nice explanation of why there is no evidence for a global warming pause

Open Mind

UPDATE: A new post at RealClimate is very relevant, and well worth the read.

One day, a new data set is released. The rumor runs rampant that it’s annual average global temperature since 1980.


Climate scientist “A” states that there is clearly a warming trend (shown by the red line), at an average rate of about 0.0139 deg.C/yr. She even computes the uncertainty in that trend estimate (using fancy statistics), and uses that to compute what’s called a “95% confidence interval” for the trend — the range in which we expect the true warming rate is 95% likely to be; it can be thought of as the “plausible range” for the warming rate. Since 95% confidence is the de facto standard in statistics (not universal, but by far the most common), nobody can fault her for that choice. The confidence interval is from 0.0098 to 0.0159 deg.C/yr. She also…

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The IPCC 2014 synthesis report was approved by the IPCC on 1st November 2014.

The draft report (i.e. still needs copy-editing and formatting) is available here, if you want to read it. It is 116 pages long. The related press release is available here:

I thought it might be useful to summarise some of the more important points of the report for anybody who is interested but doesn’t have the time or inclination to wade through the entire document.

This first blog post explains the first diagram in the report. It is in the section “Topic 1: Observed changes and their causes” and it shows the real, measured changes that have been taking place on Earth due to global warming. The report states “Warming of the climate system is unequivocal, and since the 1950s, many of the observed changes are unprecedented over decades to millennia. The atmosphere and ocean have warmed, the amounts of snow and ice have diminished, and sea level has risen.”

Figure 1.1 of the report presents 5 different sets of information – I have split the diagram up into individual parts and will explain each part separately. (Apologies for the poor quality of the diagrams – I used print screen to take them from the pdf of the report – hope the IPCC don’t mind me doing that – all images by IPCC.)

Panel (a):  Global temperature  change

Let’s start with panel (a). This shows the average temperature over time between the years 1850 and 2012. The temperature is plotted as the difference in temperature compared to the average (mean) of the years 1986–2005. So, looking at the diagram, between 1850 and 1900, the average temperature was ~ 0.6 °C colder than it was between 1986-2005, and nowadays it is about 0.2 degrees warmer than 1986-2005. The different coloured lines (black, blue and orange) correspond to different data sets and in the bottom panel, the grey boxes are an estimate of the uncertainty on the mean for one of the data sets. If you want to check out the data sources and how they are measured, the black line is data from the Met Office Hadley Centre and Climatic Research Unit, the blue line is from the NOAA (US National Oceanic and Atmospheric Administration) National Data Centre, and the orange line is from the NASA Goddard Institute. Importantly, all 3 data sets show good agreement. Annoyingly, the current report doesn’t actually list the data sets, and the links it provides in the figure caption are broken, but the same graph is shown on the Met-Office website, which lists the data sources.

The top panel shows the temperatures averaged over a single year, and you can see that yes, there is some variation – some years are colder than others. But then look at the bottom panel – this is the temperatures averaged over a decade. This is the more important diagram when you are looking at long term trends, because averaging over decades smoothes out any variability due to short-lived processes, like El Niño / El Niña events, cooling from volcanic eruptions, and temporarily reduced emissions from recessions. This bottom graph clearly shows that warming started in the early 1900s, paused during the mid 20th century, and then dramatically increased during the later part of the 20th century and into the 21st century.

Now, also consider that this data only shows up until 2012. Looking at data from the UK Metereological Office shows that average global temperature for last year, 2013, was 0.05 °C warmer than it was in 2012 and 2014 is already recording temperatures well above average (see here, here and here)

Summary: Average global temperatures are rising over time. Global warming is happening – absolutely no doubt about it!

Moving on to panel (b):

Global temperature change

This map shows which parts of the Earth are warming and which are cooling. You can see that the data set isn’t complete – we are missing much of the Arctic and Antarctic, large parts of the Pacific Ocean, and some central continental areas. These areas were excluded because the data record was less than 70 % complete and / or the first and last 10% of the time period had less than 20% data availability – i.e. the map is based on data that is robust and unlikely to be influenced by random outliers at the beginning and end of the time period. The little “+” symbols indicate grid squares where the data shows a statistically significant warming trend. Coloured squares without a “+” are not as statistically robust.  Even without a complete global map of data, we can see that most places are warming (yellow, orange, red, purple). Continental areas have warmed by as much as 2.5 °C over 111 years between 1901 and 2012. The only place that seems to have cooled  (pale blue) at all is a small patch of the north Atlantic (which I would hazard a guess is related to changes in thermohaline circulation of the Gulf Stream). The data on this map is surface temperature and it is derived from the orange data (NASA) in panel a.

Summary: The temperature rise over the last 111 years was not evenly distributed across the Earth. The vast majority of the Earth’s surface has seen a rise in temperatures.

Panel (c):

Change in Sea Ice

This shows the extent of summer Arctic sea ice since 1900 (averaged for each year over 3 months) and the extent of summer Antarctic sea ice since the late 1970s (averaged for each year over 1 month). The areal extent of summer Arctic sea ice has almost halved since the 1950s and is still reducing. At the moment the Antarctic summer sea ice looks like it hasn’t changed much, but we don’t know how extensive the ice was earlier in the 20th Century. Again, the different  coloured lines represent different data sets, and they show good agreement (at least in pattern, if not in absolute value for Antarctica). Unfortunately the links in the current draft of the IPCC report don’t work so I can’t tell you where the data comes from at the moment.

Summary: The areal extent of summer sea ice in the Arctic has almost halved since 1960.

Panel (d):

Global Sea Level Rise

This shows the change in global mean sea level between 1900 and 2010. Like panel (a), it is plotted as difference in sea level relative to the average sea level between 1986 and 2005. So, looking at the graph, back in 1900, sea level was about 0.15 m (15 cm) lower than the average for 1986–2005, and in 2010 it was about 0.05 (5 cm) higher than the average for 1986-2005. The 1986 – 2005 mean value is based on data from the longest running (i.e. most complete) data set.

Summary: Global mean sea level has risen around 20 cm since the year 1900.

Panel (e):

Change in precipitation

This map shows how on-land precipitation (rain and snow fall) has changed over time since 1951. The data used in this diagram were assessed and included using the same criteria as in panel (b) – i.e. data available for > 70% of the time period and with > 20% of the data available in the first and last 10% of the time period. The scale on this map is a bit confusing at first glance – it is precipitation in millimetres per year per decade. This isn’t an absolute change in value, like for the map in panel (b); this is plotting a change in the rate of change. In simple terms, the darkest blue shade represents areas where, every decade, the amount of precipitation has increased by 50 – 100 mm per year – i.e. the average precipitation per year between 1961-1971 was between 50 and 100 mm higher than the average precipitation per year between 1951-1961. And the average precipitation per year between 1971-1981 was between 100 and 200 mm higher than 1951-1961. Looking at the map, large parts of the African and Asian continents are drying out and seeing much less precipitation (incidentally, note the area of North Africa that hasn’t seen much change in precipitation levels – remember that this is the Sahara Desert – it can’t dry out much more…), while Northern Europe, much of the mainland USA, the east coast of South America and northern Australia are all seeing increased precipitation.

Summary: Patterns of rain and snowfall are changing, with some areas receiving much more precipitation and some receiving less.

So, that is the end of Figure 1.1 of the IPCC 2014 synthesis report.

Nice summary highlighting some of the problems with ignorance in climate science.

Critical Angle

Geologists, especially those, like me, of a certain age, often have problems with climate science and the idea that humans may be triggering a massive and abrupt change in the climate. Global change, we were taught, occurred slowly and by commonplace mechanisms: sediment carried by water, deposited a grain at a time: erosion effected by water and wind, the hardest rocks slowly ground down crystal by crystal. The great features of the Earth—the canyons, mountains and basins—were built this way and owe their grandeur to Deep Time, geology’s greatest intellectual gift to human culture. In the face of the history of the natural world, geologists feel a certain humility at the insignificance of humans and our tiny lifespans. But we also feel some pride in the role of our subject in piecing together this history from fossils and outcrops of rock. It’s an amazing detective story: diligent scientists patiently working…

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Interesting article regarding a major challenge for the renewables industry – when storing energy ultimately costs more energy.

Brave New Climate

Pick up a research paper on battery technology, fuel cells, energy storage technologies or any of the advanced materials science used in these fields, and you will likely find somewhere in the introductory paragraphs a throwaway line about its application to the storage of renewable energy.  Energy storage makes sense for enabling a transition away from fossil fuels to more intermittent sources like wind and solar, and the storage problem presents a meaningful challenge for chemists and materials scientists… Or does it?

Guest Post by John Morgan. John is Chief Scientist at a Sydney startup developing smart grid and grid scale energy storage technologies.  He is Adjunct Professor in the School of Electrical and Computer Engineering at RMIT, holds a PhD in Physical Chemistry, and is an experienced industrial R&D leader.  You can follow John on twitter at @JohnDPMorgan First published in Chemistry in Australia .

Several recent analyses of the…

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I enjoyed reading this account of an astrobiology field trip to some of Iceland’s least accessible areas. I’m also very jealous 🙂

dr. claire cousins

Landing into Keflavik airport has become a familiar sight, as the vast flat expanse of moss-covered lava flows stretches out into a horizon of cold grey clouds as we approach the runway. This is my ninth trip to Iceland, and for this trip we are sampling from various sites in the northeast – some old, some new. Our key target as always is Kverkfjoll – a dormant volcanic caldera that peeks out from the northern margin of Vatnajokull ice cap. Iceland is often referred to as ‘the land of ice and fire’, and the geothermal environments at the summit of Kverkfjoll epitomise this name. Here, scattered clusters of small fumaroles – which vent hot volcanic gas – interact with overlying ice and snow to produce localised and short-lived pools of geothermal meltwater, which provide a haven for microbes within an otherwise remote and frozen environment. These environments provide a fascinating analogue to hydrothermal environments…

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