Posts Tagged ‘Climate Change’

Air Temperature

April 1, 2018

Recently, two disparate strands of my work produced publications within a week of each other.

Curiously they both concerned one of the commonest measurements made on Earth today – the measurement of air temperature.

  • One of the papers was the result of a humbling discovery I made last year concerning a common source of error in air temperature measurements. (Link to open access paper)
  • On the other  paper I was just one amongst 17 authors calling for the establishment of global reference network to monitor the climate. My guess is that most people imagine such a network already exists – but it doesn’t! (Link to open access paper)

I am writing this article because I was struck by the contrasting styles of these papers: one describing an arcane experimental detail; and the other proposing a global inter-governmental initiative.

And yet the aim of both papers was identical: to improve measurement so that we can more clearly see what is happening in the world.

Paper 1

In the middle of 2018 I was experimenting with a new device for measuring air temperature by measuring the speed of sound in air.

It’s an ingenious device, but it obviously needed to be checked. We had previously carried out tests inside environmental chambers, but the temperature stability and uniformity inside the chambers was not as good as we had hoped for.

So we decided to test the device in one of NPL’s dimensional laboratories. In these laboratories, there is a gentle, uniform flow of air from ceiling to floor, and the temperature is stable to within a hundredth of a degree Celsius (0.01 °C) indefinitely.

However, when I tried to measure the temperature of the air using conventional temperature sensors I got widely differing answers – varying by a quarter of a degree depending on where I placed the thermometer. I felt utterly depressed and humiliated.

Eventually I realised what the problem was. This involved stopping. Thinking carefully. And talking with colleagues. It was a classic case of eliminating the impossible leaving only the improbable.

After believing I understood the effect, I devised a simple experiment to test my understanding – a photograph of the apparatus is shown below.

tubes-in-a-lab-photo.png

The apparatus consisted of a set of stainless steel tubes held in a clamp stand. It was almost certainly the cheapest experiment I have ever conducted.

I placed the tubes in the laboratory, exposed to the downward air flow, and  left them for several hours to equilibrate with air.

Prior to this experience, I would have bet serious amounts of money on the ‘fact’ that all these tubes would be at the same temperature. My insight had led me to question this assumption.

And my insight was correct. Every one of the tubes was at a different temperature and none of them were at the temperature of the air! The temperature of the tubes depended on:

  • the brightness of the lights in the room – which was understandable but a larger effect than I expected, and
  • the diameter of the tubes – which was the truly surprising result.

Results 1

I was shocked. But although the reason for this is not obvious, it is also not complicated to understand.

When air flows air around a cylindrical (or spherical) sensor only a very small amount of air actually makes contact with the sensor.

Air reaching the sensor first is stopped (it ‘stagnates’ to use the jargon). At this point heat exchange is very effective. But this same air is then forced to flow around the sensor in a ‘boundary layer’ which effectively insulates the sensor from the rest of the air.

Air flow

For small sensors, the sensor acquires a temperature close to that of the air. But the air is surprisingly ineffective at changing the temperature of larger sensors.

The effect matters in two quite distinct realms.

Metrology

In metrology – the science of measurement – it transpires that knowledge of the temperature of the air is important for the most accurate length measurements.

This is because we measure the dimensions of objects in terms of the wavelength of light, and this wavelength is slightly affected by the temperature of the air through which the light passes.

In a dimensional laboratory such as the one illustrated below, the thermometer will indicate a temperature which is:

  • different from the temperature of artefacts placed in the room, and
  • different from the temperature of the air.

Laboratory

Unless the effect is accounted for – which it generally isn’t – then length measurements will be slightly incorrect.

Climatology

The effect is also important in climatology. If a sensor is changed in a meteorological station people check that the sensor is calibrated, but they rarely record its diameter.

If a calibrated sensor is replaced by another calibrated sensor with a different diameter, then there will be a systematic effect on the temperatures recorded by the station. Such effects won’t matter for weather forecasting, but they will matter for people using the stations for a climate record.

And that brings me to Paper 2

Paper 2

Hadcrut4 Global Temperature

When we see graphs of ‘global temperatures’ over time, many people assume that the data is derived from satellites or some ‘high-tech’ network of sensors. Not so.

The ‘surface’ temperature of the Earth is generally estimated in two quite distinct parts – sea surface temperature and land surface temperature. But both these terms are slight misnomers.

Considering just the land measurements, the actual temperature measured is the air temperature above the land surface. In the jargon, the measurement is called LSAT – the Land Surface Air Temperature.

LSAT is the temperature which human beings experience and satellites can’t measure it.

LSAT data is extracted from temperature measurements made in thousands of meteorological stations around the world. We have data records from some stations extending back for 150 years.

However, it is well known that data is less than ideal: it is biased and unrepresentative in many ways.

The effect described in Paper 1 is just one of many such biases which have been extensively studied. And scientists have devised many ways to check that the overall trend they have extracted – what we now call global warming – is real.

Nonetheless. It is slightly shocking that a global network of stations designed specifically with the aim of climate monitoring does not exist.

And that is what we were calling for in Paper 2. Such a climate network would consist of less than 200 stations world-wide and cost less than a modest satellite launch. But it would add confidence to the measurements extracted from meteorological stations.

Perhaps the most important reason for creating such a network is that we don’t know how meteorological technology will evolve over the coming century.

Over the last century, the technology has remained reasonably stable. But it is quite possible that the nature of data acquisition for meteorological applications will change  in ways we cannot anticipate.

It seems prudent to me that we establish a global climate reference network as soon as possible.

References

Paper 1

Air temperature sensors: dependence of radiative errors on sensor diameter in precision metrology and meteorology
Michael de Podesta, Stephanie Bell and Robin Underwood

Published 28 February 2018
Metrologia, Volume 55, Number 2 https://doi.org/10.1088/1681-7575/aaaa52

Paper 2

Towards a global land surface climate fiducial reference measurements network
P. W. Thorne, H. J. Diamond, B. Goodison , S. Harrigan , Z. Hausfather , N. B. Ingleby , P. D. Jones ,J. H. Lawrimore , D. H. Lister , A. Merlone , T. Oakley , M. Palecki , T. C. Peterson , M. de Podesta , C. Tassone ,  V. Venema, K. M. Willett

Published: 1 March 2018
Int. J. Climatol 2018;1–15. https://doi.org/10.1002/joc.5458

3. Light transmission through the atmosphere

January 3, 2017

co2_band_formation

In part 2 I looked at transmission of infrared light through a gas containing a molecule which absorbs infrared light at one particular frequency.

We saw that at higher concentrations, the absorption at specific frequencies broadened until entire bands of frequencies were ‘blocked’.

We saw that the width of the ‘blocked bands’ continued to increase with increasing concentration.

Here we look at how that insight can be applied to transmission of infrared light through Earth’s atmosphere.

This is even more complicated.

  • We are mainly interested in transmission of infrared light from the Earth’s surface out through the atmosphere and into space, but the atmosphere is not at a uniform temperature or pressure.
  • When absorbing gases are present, the air is not just a ‘conduit’ through which infra-red light passes – the air becomes a source of infrared radiation.
  • We are mainly interested in the effect of carbon dioxide – but there are several other infrared ‘active’ gases in the atmosphere.
  • Gases are not the only thing in the atmosphere: there is liquid water and particulates.

So it’s complicated: Here are a few more details.

1. Density.

If the carbon dioxide is distributed in a fixed proportion to the amount of oxygen and nitrogen through the atmosphere, then it will have more effect where the atmosphere is most dense: i.e. lower down in the atmosphere.

And density is affected by both temperature and pressure.

Since carbon dioxide molecules absorb 100% of the infrared light with wavelengths around 15 micrometres, as we saw in the previous article, increasing the concentration of carbon dioxide increases the range of wavelengths that are ‘blocked’. This is illustrated in the figure at the head of the article.

Increasing the concentration of carbon dioxide also changes the height in the atmosphere at which absorption takes place.

2. Re-radiation.

Once absorbed by a carbon dioxide molecule, the infrared light does not just disappear.

It increases the amplitude of vibration of the molecule and when the molecule collides with neighbouring molecules it shares that energy with them, warming the gas around it.

A short while later the molecule can then re-radiate light with the same frequency. However the brightness with which the gas ‘glows’ relates to its local temperature.

Some of this re-radiation is downward – warming the Earth’s surface – and giving rise to a ‘greenhouse’ effect.

And some of this re-radiation is upward – eventually escaping into space and cooling the Earth.

3. Other things.

Carbon dioxide is not only the infrared active gas in the atmosphere. There is also methane, ozone and, very significantly, water vapour.

There is also condensed water – clouds.

And then there are particulates – dust and fine particles.

All of these affect transmission of light through the atmosphere to some extent.

For an accurate calculation – all these effects have to be considered.

MODTRAN

Fortunately, the calculation of transmission through the atmosphere has been honed extensively – most notably by the kind people at the  US Air Force.

However the code is available for anyone to calculate atmospheric transmission.

David Archer and the University of Chicago kindly host a particularly friendly front end for the code.

modtran-web-interface

Aside from just clicking around, it is possible to download the results of the calculations and that is how I plotted the graphs at the head of the page.

To get that data I removed all the other greenhouse gases from the atmosphere (including water), and varied only the concentration of carbon dioxide.

Notice that the absorption lines grow into bands that continue to broaden as we add more and more  carbon dioxide. This is exactly what we saw in the simple model in the second article.

This shows that the transmission through the atmosphere is still being affected by additional carbon dioxide, and these bands have not ‘saturated’.

Asking a question

MODTRAN can answer some interesting questions.

Assuming that the Earth’s surface is at a temperature of 15 °C, we can ask MODTRAN to calculate how much infrared light leaves the top of the atmosphere (100 km altitude) as we add more carbon dioxide. The result of these calculations are shown below:

toa-radiative-power

The first thing to notice is the qualitative similarity between this graph – the result of complex and realistic calculations – with the simple spreadsheet model I showed in the second article.

The second thing to notice is that the calculations indicate that increasing the concentration of carbon dioxide in the atmosphere reduces the amount of radiation which escapes at the top of the atmosphere. And that it will continue to do so even as the concentration of carbon dioxide increases well beyond its current 400 parts per million (ppm).

Where does that absorbed radiation go? The graph below shows the results of another calculation. It imagines being on the ground and asks how much infrared light is re-radiated back to the Earth’s surface as the concentration of carbon dioxide increases.

downward-flux-graph

The graph shows that matching the decline in infrared radiation leaving the top of the atmosphere, there is a matching increase in radiation falling back down to Earth.

Importantly, both these effects still depend on the concentration of carbon dioxide in the atmosphere even as the concentration grows past 400 ppm.

Over the longer term, this increase in downward radiation will increase the temperature of the Earth’s surface above the assumed 15 °C. This process will continue until the outgoing radiation leaving the top of the atmosphere is balanced with the incoming solar radiation.

That’s all for this article:

In this article we saw that transmission of infrared light through the atmosphere is complicated.

Fortunately MODTRAN software can cope with many of these complexities.

The conclusions of our calculations with MODTRAN are similar to conclusions we came to in the previous article.

Increasing the concentration of a molecule such as carbon dioxide which absorbs at a single frequency will continue to reduce transmission through the atmosphere indefinitely: there is no limit to the amount of absorption.

The next article is about the conclusions we can draw from these calculations.

When will the North Pole become the North Pool?

December 16, 2016

arctic_ssi_201612_chart

It is a sad fact, but it is likely that within my lifetime it will become possible to sail to the North Pole. I am 56.

Tragically it is also true that there is absolutely nothing that you or I can do about it.

In fact, even in the unlikely event that humanity en masse decided it wanted to prevent this liquefaction, there would be literally nothing we could do to stop it.

The carbon dioxide we have already put in the atmosphere will warm the Earth’s surface for a few decades yet even if we stopped all emissions right now.

Causation

The particular line of causation between carbon dioxide emissions and warming of the arctic is long, and difficult to pin down.

Similarly it is difficult to determine if a bull in a china shop broke a particular vase, or whether it was a shop helper trying to escape.

Nonetheless, in both cases the ultimate cause is undeniable.

What does the figure show?

The animation at the head of the page, stolen from NASA’s Earth Observatory, is particularly striking and clear.

The animation shows data from 1979 to this past November 2016 showing the extent of sea ice versus the month of year.

Initially the data is stable: each year is the same. But since the year 2000, we have seen reductions in the amount of sea ice which remains frozen over the summer.

In 2012, an additional one million square kilometres – four times the area of England Scotland and Wales combined – melted.

The summer of 2016 showed the second largest melt ever.

The animation highlights the fact that the Arctic has been so warm this autumn, that Sea Ice is forming at an unprecedentedly slow rate.

The Arctic Sea Ice extent for November 2016 is about one million square kilometres less than what we might expect it to be at this time of year.

My Concern 

Downloading the data from the US National Snow and Ice Data Centre, I produced my own graph of exactly the same data used in the animation.

The graph below lacks the drama of the animated version at the head of the article. But it shows some things more clearly.

sea-ice-december-2016-graph

This static graph shows that the minimum ice extent used to be stable at around 7 ± 1 million square kilometres. The minimum value in 2012 was around half that.

The animated graph at the head of the article highlights the fact that the autumn freeze (dotted blue circle) is slower than usual – something which is not clear in the static graph.

My concern is that if this winter’s freeze is ‘weak’, then the ice formed will be thin, and then next summer’s melt is likely to be especially strong.

And that raises a big question at the very heart of our culture.

When the North Pole becomes the North Pool, where will Santa live?

 

Global Warming Trends

December 3, 2016

 

The anomaly in the Earth's temperature based only on thermometers in meteorological stations and excluding the oceans which cover about 70% of the Earth's surface. The Daily Mail only draw your attention to a small fraction of the data - and they include monthly fluctuations which disguise the clear warming trend.The anomaly in the Earth’s temperature based only on thermometers in meteorological stations and excluding the oceans which cover about 70% of the Earth’s surface. The Daily Mail only draw your attention to a small fraction of the data – and they include monthly fluctuations which disguise the clear warming trend.

Why do I ever even look at the Daily Mail website?

The other day I came across this pernicious article purporting to describe a plummeting of global temperatures above the land surfaces of the Earth. The article states:

Global average temperatures over land have plummeted by more than 1C since the middle of this year – their biggest and steepest fall on record. [P.S. by 1C they mean 1 °C not 1 coulomb]

The news comes amid mounting evidence that the recent run of world record high temperatures is about to end.

Some scientists, including Dr Gavin Schmidt, head of Nasa’s climate division, have claimed that the recent highs were mainly the result of long-term global warming.

Others have argued that the records were caused by El Nino, a complex natural phenomenon that takes place every few years, and has nothing to do with greenhouse gas emissions by humans. The new fall in temperatures suggests they were right.

It is accompanied by a misleading graphic:

Graphic from the Daily Mail website. Notice their graph only runs from 1997 and includes large fluctuations due to sub-annual changes. It describes only the changes in temperature above the land surfaces of the Earth.

Graphic from the Daily Mail website. Notice their graph only runs from 1997 and includes large fluctuations due to sub-annual changes. It describes only the changes in temperature above the land surfaces of the Earth.

The article is nonsense from start to finish, but I just thought I would show you how to get at the data for yourself so you can make up your own mind.

Decide for yourself

This excellent NASA web page allows you plot various graphs of temperature data, and change the degree of smoothing applied to the raw data. I invite you to try it out for yourself.

This NASA web page has excellent links and descriptions

You can choose to include land stations only, or combine land and ocean data. Remember that the land surface of the Earth represents less than 30% of our planet’s surface, and so the most relevant measure of global warming involves both land and ocean data.

As well as generating graphs, you can use the website to download data and then graph the data in Excel™ as I have done for the graph at the top of the page.

I don’t fully understand where the data in the Daily Mail graphic comes from. They appear to have picked only recent data and included monthly data rather than annual averages to increase the noise and de-emphasise the obvious trend in the data.

The background colouration in the Daily Mail graphic implies that the high temperatures are all associated with the El Nino conditions. This is not correct. As the graphic below (from skeptical science) shows, years with and without an El Nino are all showing a warming trend.

An animated file showing global surface temperatures in El Nino years, La Nina years, and neutral years. The graphic is from sceptical science.

An animated file showing global surface temperatures in El Nino years, La Nina years, and neutral years.

For the technically-minded reader, this article from Victor Venema may help.

The Trend 

What struck me as shocking was what happened when I set the smoothing of the data to 20 years – so that the trend represented a trend in climate rather than annual or multi-annual fluctuations.

In the figure below I show the data for the land and ocean mean temperature anomaly and the red line shows the smoothing with a 20-year running average. Since 1980 – which was 36 years ago – the data is essentially a straight line.

The estimated change in the temperature of the air above the oceans and the land. The red line shows a smoothed version of the annual data with a 20-year window to reflect changes in climate rather than the internal fluctuations of the Earth's complex weather systems. Source: NASA-GISS: see article for detailsThe estimated change in the temperature of the air above the oceans and the land. The red line shows a smoothed version of the annual data with a 20-year window to reflect changes in climate rather than the internal fluctuations of the Earth’s complex weather systems. Notice that since 1980 , the smoothed line is essentially straight with a gradient of approximately 0.017 °C per year. Source: NASA-GISS: see article for details

What if…

Friends, just suppose that NASA had spotted not a global warming trend, but an asteroid headed straight for Earth. Suppose they calculated it would not destroy civilisation, but it would nonetheless be devastating: its tidal disturbance would cause widespread floods

Would we want to know? Well Yes!

Now suppose that the entire world got together in, say, Paris, and developed a plan to deflect the asteroid. The plan would be expensive and risky – costing about 1% of global GDP – but after about 100 years of effort we would be freed from the risk of a collision.

Would we follow the plan? Well Yes!

Friends, Global warming is equivalent in its impact to an asteroid headed to Earth, and the Paris Accord, while inadequate in itself, represents the start of a plan in which the disparate governments of Earth have agreed to slow development (that brings direct benefit to their citizens) in order to tackle this threat.

Please don’t let the Daily Mail deceive you into thinking global warming is not happening: it is. It is happening slowly – 0.017 °C per year  – and the odd year of inaction makes no difference.

But year upon year of inaction condemns us to a fate that is out of our control.

 

Hope

July 21, 2015
Map of the world showing regions that in June 2015  were warmer or cooler than they 'normally' are. Dark red shows record warm regions. Source NCDC - see text for link. Click image for a larger version.

Map of the world showing regions that in June 2015 were warmer or cooler than they ‘normally’ are. Dark red shows record warm regions. Most of the Earth is warmer than it has been historically. Remember that June is the height of Southern Hemisphere winter. Source NCDC – see text for link. Click image for a larger version.

Sometimes it is difficult to stay hopeful.

And the NCDC ‘State of the Climate’ report for June 2015 is so shocking that I really should feel no hope at all.

What does it say to put me in such a mood? Well it is authoritative and detailed, but here’s a taster.

June 2015 also marks the fourth month this year that has broken its monthly temperature record, along with February, March, and May. The other months of 2015 were not far behind: January was second warmest for its respective month and April was third warmest. These six warm months combined with the previous six months (four of which were also record warm) to make the period July 2014–June 2015 the warmest 12-month period in the 136-year period of record, surpassing the previous record set just last month (June 2014–May 2015). … the 10 warmest 12-month periods have all been marked in the past 10 months.

In short, the surface temperature of the Earth is dramatically warm and it looks likely that the calendar year 2015 will be the hottest ever.

And yet I feel hopeful. Why?

Because this is how the Daily Mail reported this news (Link)

June warmest EVER recorded globally as forecasters warn 2015 set to be a record breaking year

That’s right, the Daily Mail reported this as a completely straight news story. It is not spun. It is not used to imply that Climate Scientists are corrupt or left-wing. No jokes are made about hiatuses or the growth of arctic sea ice.

I honestly never thought I would live to see the day that the Daily Mail reported serious climate change news as serious climate change news. And yet here it is.

If newspapers such as the Daily Mail can really break their links with climate change deniers then the fear, uncertainty and doubt that they spread will begin to dissipate. And then we can all get busy actually solving problems rather than arguing.

It’s one reason to be hopeful. And for now, that’ll do.

================

The Figure is from NOAA National Centers for Environmental Information, State of the Climate: Global Analysis for June 2015, published online July 2015, retrieved on July 20, 2015 from http://www.ncdc.noaa.gov/sotc/global/201506.

Cultural Vertigo

December 15, 2012
London at night from the air

London at night from the air. The roads look the veins and arteries of a living being.

ver·ti·go (Noun): A sensation of whirling and loss of balance, associated particularly with looking down from a great height, or caused by disease…

I have known for some time that I suffer from two forms of vertigo. The first is the normal form, induced by looking down over the edges of cliffs or tall buildings: I have to believe that this perfectly normal.

The second is age vertigo which involves similar dizziness, nausea and panic, but is induced by meeting adults who are much younger than me. My head spins as I focus on the vastness of the gap separating me from them – a gap across which we can converse, but not traverse. I cannot travel back to meet them, and by the time they reach my place on the cliff-face of life, I will have moved on. Or fallen off.  To the best of my knowledge I am the originator of this description of this sensation which must be surely be commonplace amongst those who are 52-ish.

Last night, as I flew back from a work visit to the European Space Agency in the Netherlands, I was visited by a third incarnation of vertigo – cultural vertigo.

The night was clear and I could see lights in towns from Holland to Belgium. On arriving above London the plane circled over the eastern edge of the M25. The view was astonishing: the roads resembled the arteries and veins of a living being – a being of unimaginable size and with an unimaginable appetite.

My sense of dizziness at the grandness and precariousness of our city was added to by the fact that I was observing this from a plane – and there was a queue of half a dozen similar observatories visible in the air behind us.

In addition to my flight, almost everything I could see below me involved burning carbon: for heating on this chilly night: for electricity to keep the lights on: and for fuel for the cars and lorries. The vastness of the city and the intensity and voracity of its need to burn carbon induced dizziness and panic. Will we ever give up our dependence on carbon? I realised I needed to add ‘despair’ to the list of characteristic symptoms of cultural vertigo.

My only relief came from remembering that we had just flown over the London Array – an offshore wind farm – visible as a regular array of red lights against the blackness of the North Sea. Surely if our culture could create and sustain this vast city – and yet realise it needed to change and create offshore wind farms – then surely we can change our ways.

In the same way that nobody envisaged London growing as large and as energy intensive as it has grown – surely we could imagine a world in which our renewable energy infrastructure grew until it met our needs. Surely we could imagine that?

Carbon Emissions: Stating the obvious

December 3, 2012
Since the dawn of time we have emitted approximately 1271 billions tonnes of carbon dioxide and we show no signs of slowing down. In 2008 we emitted approximately 32 billion tonnes of carbon dioxide. The BBC figure for 2012 is 35.6 billion tonnes.

Since the dawn of time we have emitted approximately 1271 billions tonnes of carbon dioxide and we show no signs of slowing down. In 2008 we emitted approximately 32 billion tonnes of carbon dioxide. The BBC figure for 2012 is 35.6 billion tonnes.

Friends – I am barely keeping my head above water – work has never been busier – and there never seems to be a moment to reflect on things. But it is quarter-to-midnight on Sunday, and even though I have just spent several hours answering the Protons for Breakfast feedback, I feel like have a few more minutes of attention in me.

This week Protons for Breakfast was about Global Warming, and as I was answering the feedback I looked up the latest data on carbon dioxide emissions. By chance the BBC covered the same story with more recent data and the gloriously obvious headline

Carbon emissions are ‘too high’ to curb climate change

The numbers are astounding. Each year we collectively emit more than 1% of the total amount of carbon dioxide in the atmosphere. And an annual figure of 35 billion tonnes is an almost inconceivably large amount of ‘stuff’. If we wanted to do this for some other reason – then the task would seem overwhelming!

I got the impression that people at Protons for Breakfast really wanted to do something about this phenomenon – but they wanted guidance as to what would make a difference!. At it is at times like this that it is worthwhile to remember the words of Mahatma Ghandi who said:

“You may never know what results come of your actions, but if you do nothing, there will be no results.”

I wish I could find something more inspiring to say. I do feel that people’s consciousness is changing, and it does seem inevitable that we will – eventually – begin to face up to this problem. At some point in time, the graph at the top of the page will peak – and we will begin move beyond the carbon age. Let’s hope it is sooner rather than later.

I told you so

October 20, 2012
In 1981 Hansen et al made predictions for the change in global mean temperature expected over the course of the coming century. The figure shows their predictions along side 4 independent estimates of what has actually happened.

In 1981 Hansen et al made predictions for the change in global mean temperature expected over the course of the coming century. The figure shows their predictions along side four independent estimates of what has actually happened.

According to Gore Vidal, the four most beautiful words in the English language are “I told you so”. My hero James Hansen can justifiably speak those words, but I am sure they don’t feel beautiful to him.

In 1981, together with six NASA colleagues, he published a paper in Science magazine entitled ‘Climatic Impact of Increasing Atmospheric Carbon dioxide‘. Science magazine won’t let you read it but it is available online here. The paper is not that difficult to understand and if you are curious about these things, it’s a good read. I particularly liked the inclusion of a simple analogy:

“The surface temperature resulting from the greenhouse effect is analogous to the depth of water in a leaky bucket with constant inflow rate. If the holes in the bucket are reduced slightly in size the water depth and water pressure will increase until the flow rate out of the holes once again equals the inflow rate. Analogously, if the atmospheric infrared opacity  increases, the temperature of the surface and the atmosphere will increase until the emission of radiation from the planet again equals the absorbed solar energy.”

The figure at the top of the page shows Figure 6 from their paper on which I have overlaid four independent estimates of what has actually happened since then. At the time the paper was published,  global mean temperature was declining and the predictions were thus extremely bold. However, looking back the authors predictions now seem conservative. And indeed the authors were careful and conservative, though clear about specific predictions.

In the summary they state

“Potential effects on the climate in the 21st Century include the creation of drought-prone regions in North America and central Asia … erosion of the West Antarctic Ice Sheet … and an opening of the fabled NorthWest passage”

Well, North America has been prone to drought, and the North West passage now regularly opens in summer. Thankfully the West Antarctic Ice Sheet seems relatively stable.

All through the paper the authors consider the uncertainties arising from the simplicity of their model and the many poorly-understood effects – such as cloud cover and solar variability – which affect climate. However, they test their predictions against plausible variations in these factors and find that the predictions of warming are robust against a wide range of plausible feedback effects. They conclude with a wider non-scientific perspective

Political and economic forces affecting energy use and fuel choice make it unlikely that the CO2 issue will have a major impact on energy policies until convincing observations of global warming at in hand. In light of historical evidence that it takes several decades to complete a major change in fuel use this makes large climate change almost inevitable.

However the degree of warming will depend strongly on the energy growth rate and the choice of fuels for the next century. Thus CO2 effects on climate may make full exploitation of coal resources undesirable. An appropriate strategy may be to encourage energy conservation and develop alternative energy sources while using fossil fuels as necessary during the next few decades.

The Climate change induced by anthropogenic release of CO2 is likely to be the most fascinating global geophysical experiment that man will ever conduct. The scientific task is to help determine the nature of future climatic effects as early as possible. The required efforts in global observations and climate analyses are challenging, but the benefits from improved understanding of climate will surely warrant the work involved.

To me these views seem modest, realistic and optimistic. But I bet that although James Hansen and his colleagues predicted the climate 30 years ahead, they never guessed that in the 21st Century the US would have senators such as Paul Brown.

To understand such ignorance we have to turn again to Gore Vidal:

The United States was founded by the brightest people in the country – and we haven’t seen them since.

Acknowledgement: This article is based on a blog story at Real Climate:

Denial in Action

September 23, 2012
Interesting Map showing the different 'seas' within the Arctic Ocean. Source NSIDC

Interesting Map showing the different ‘seas’ within the Arctic Ocean. Source NSIDC

The collapse in the extent of the summer minimum of Arctic Sea Ice has been a shock to everyone, but in honesty, not really a surprise. But disappearance of three-quarters-of-a-million square kilometres of sea ice seemed to be such a dramatic change that I was sure that Climate Change ‘sceptics’ would be holding up their hands and saying simply ‘I was wrong’. So I headed over to the Sea Ice Update pages of Antony Watts ‘Watts Up’ site to witness their surrender.

But far from admitting that their world view was flawed, the ‘Climate Sceptics’ were responding in a manner which would be hilarious if it were not so tragic. The discussion is a classic example of a group unable to ‘distinguish the forest from the trees’. The discussion is focussed on individual facts (the trees) which are discussed in detail and critically examined. But they denounce anyone who raises the wider context of the facts (the forest) i.e. the only theory which predicted sea-ice melting. Indeed our concerns that this might happen are the very reason that the sea-ice data exists.

The page begins with a section noting that:

…there are some quite large Sea Surface Temperature Anomalies in the Arctic at present [up to 7 °C]. They appear to centered in four primary areas, the coasts of the Beaufort, Laptev and Kara Seas, as well as the middle of Baffin Bay. There are a multitude of potential explanations for these anomalies, let’s take them individually

We then get the individual potential explanations which I will summarise:

  1. Could be due to the low sea ice extent which means areas previously covered with ice are now exposed.
  2. Could be due to an ‘unusually strong storm’ which occurred early in August which could have broken up the ice cover.
  3. Could be Albedo Feedback – the replacement of reflective sea ice with dark ocean – likely to be a factor.
  4. Could be anthropogenically-warmed river discharges – quite likely a factor in some areas.
  5. Could be Northern Polar Lower Troposphere Anomalies – basically the air temperature has warmed over the decades, but enough for the trend to explain the sea surface temperature anomalies.
  6. Could be Tundra Vegetation Feedback – where the sea ice has retreated plants have begun to grow, changing surface albedo.

I have summarised these explanations but each one is discussed in detail. The discussions then cover other possible explanations:

  • Arctic Drilling
  • Undersea Volcanos
  • Soot from Chinese Coal Power Stations
  • The effect of the North Atlantic Oscillation – a persistent weather pattern with two distinct stable states.
  • Absorption of Energy from Geomagnetic Storms
  • Increased use of icebreakers and even tourist boats.
  • There has been no extra melting – just dispersal of sea ice into smaller pieces which are not counted as contiguous sea ice.

All these are discussed intelligently, helpfully and politely. It is an admirable example of a community of interested people discussing a topic. But when someone suggests:

There’s the increased release of anthropogenic greenhouse gases, such as CO2.

they are quickly told…

OK, you made a conjecture. Now, show a direct connection between Arctic ice melt and anthropogenic CO2, per the scientific method: testable, and using raw data. Otherwise, you have just expressed an opinion, nothing more.

In short – we don’t want to know about this.

In fact Climate models – our way of taking account of as many factors as we can think of – predicted long ago that Arctic warming would result from CO2 emissions. And Arctic warming can be reasonably expected to thin the ice sheet over the Arctic Ocean, which will then break up when there is a storm. All of the factors mentioned above may be proximate causes of the ice break up and enhanced sea-surface temperatures. But in fact the ultimate cause is in all probability the emission of greenhouse gases.

What we learn is that this group of well-meaning, interested and intelligent people simply rejected the most likely cause of this astonishing phenomenon. It caused me to wonder, if  there were any event which would cause these people – not perhaps to change their minds – but to perhaps shift their opinion slightly. To consider that perhaps all the world’s experts in Climate studies might just have a point worth considering?

Cosmic Rays and Climate Change

August 31, 2011
Clouds - condensed water vapour - formed around tiny particles emitted from jet engines

Clouds - condensed water vapour - formed around tiny particles emitted from jet engines. Do cosmic rays give rise to similar 'contrails' that initiate the growth of clouds? Click for larger version

Cosmic rays are the particles (probably protons and not ‘rays’ at all) that are ejected from extreme events throughout our galaxy and beyond, that bombard the Earth from all directions. I discussed the basic phenomenology and the fantastic satellite recently launched to study them here. This article is about recent stories reporting a link between cosmic ray flux and the formation of water droplets in the atmosphere -clouds. Various articles describing the research can be found here:

Water molecules in the atmosphere have quite different effects depending on whether they are present as droplets – i.e. in a cloud – or as isolated molecules i.e. water vapour. In either form they have roughly similar effects on infra red light emitted by the Earth, but as we all know, clouds block visible light. The process by which droplets form has been the object of extensive study for more than a century – one of the major effects affecting the stability of droplets is called the Kelvin effect – and yet still we do not collectively understand how water vapour condenses in the atmosphere to form cloud droplets.

Of course we don’t know nothing, but even though the process of droplet formation is ubiquitous and important, the process is complex. The most significant fact is that even when there is more than enough water vapour in the air to form liquid droplets (so-called super-saturated air) they just don’t form by themselves. The chance of the water molecules clumping together by chance is infinitesimal. In practice, they need a ‘seed’ of some kind which allows water molecules to stick to it and which forms the ‘nucleus’ of a droplet which can grow.

CERN's Illustration of the process of droplet formation

CERN's Illustration of the process of droplet formation. Click for larger version. Courtesy CERN

The research from CERN (who can generate proton beams very easily) evaluated the effect of cosmic rays (i.e. fast protons) on the formation of the smallest droplets under different simulated atmospheric conditions and in the presence of different impurities. The results were complex, but can be divided into two parts:

  • When simulating the atmosphere at an altitude of 1 kilometer (3000 feet) where the temperature is approximately -10 °C (prime cloud forming temperature) , they were surprised to find that the rate of droplet formation was only one thousandth of  that observed in the real atmosphere, with or without the ‘cosmic ray’ bombardment.
  • When simulating the atmosphere at an altitude of 5 kilometers (16000 feet) where the temperature is approximately -25 °C – they found that ‘cosmic ray’ bombardment enhanced the rate of tiny droplet formation by a factor 10.
So the results indicate that droplet formation is even more complex than had been previously considered. But as many reports were at pains to point out, this is not really news because nobody ever thought they understood the process in the first place! And the droplets formed in the experiment were still too small to grow into cloud droplets and scatter light. Small droplets – perhaps 10 nanometers (50 atoms) do not necessarily grow to be large 1 micron size droplets typically found in clouds. Small droplets tend to evaporate faster than larger droplets and so when there is a mix of droplet sizes, small droplets tend to shrink and larger ones tend to grow – that is a manifestation of the Kelvin effect I mentioned above. However, no doubt we will eventually figure out how the process works.
However, I would like to single out the disingenuous Andrew Orlowski who writes for the Register for special castigation. Mr. Orlowski is an iconoclast who enjoys mocking the achievements of others. From reading his articles it is cleat that Mr. Orlowski objects to the idea that anthropogenic carbon dioxide emissions could conceivably be affecting the climate. So Mr Orlowski loves the idea that Cosmic Rays could be affecting the climate because they are ‘not our fault’ and we can just ignore the ‘liberal whingers’ calling for controls on energy usage. I don’t know why he so persistently rejects the idea that carbon dioxide emissions could be affecting the climate, because its a pretty sound idea with quite a lot of evidential and theoretical support. But every report he writes on the subject focuses on the things which people can’t explain and implies that the whole concept is thought up by a liberal/authortarian elite who – unlike the free-thinking Mr Orlowski – are unwilling to accept new data. However he never has the honesty to state what he actually thinks. So, for example,  he ends his article with a quote implying that the lead author thinks that previous climate studies are bunkum.
When Dr Kirkby first described the theory in 1998, he suggested cosmic rays “will probably be able to account for somewhere between a half and the whole of the increase in the Earth’s temperature that we have seen in the last century.”
But in fact the actual results of Dr. Kirkby’s work are completely inconclusive – telling us only what we knew before – that we don’t understand the basic process of cloud formation.
As new research fills in the gaps in our knowledge of the many complex factors that affect our climate, many media sources invite us to view the work in an essentially confrontational light. The question they ask is whether this report strengthens the views of climate change ‘skeptics’ or climate change ‘supportors'(!). Frequently one voice from each camp will be quoted to further this sense of antagonism. But in fact there will always remain many areas of uncertainty and we – you and I and scientists and governments – have to cope with this uncertainty. We have to make our Climate Models as best we can even though we don’t understand all the elements: We have to make decisions about energy usage and generation (Wind turbines, Electricity pylons, banned light bulbs) in the face of this uncertainty. These decisions  are difficult enough in themselves and we would all do better without this kind of tribal response to each new piece of information.

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