Looking Back at Our Ancient Climate

Climate Change Challenges MOOC (2)
This week started with Professor Tim Lenton taking a look into deep time and the early state of planet earth.
In the beginning, well pretty early on anyway, the sun was much cooler than it is today, it was 25% -30% less bright so one would imagine the earth’s temperature would be much cooler but in fact it was actually warmer than today. This was due to a rather thicker blanket of greenhouse gasses, later some of these gases were slowly removed over time by the action of the carbon cycle.

(Professor Tim doesn’t like ‘greenhouse’ terminology but the rest of the world still uses it so it has become something of a lingua franca.)

The carbon cycle extracts carbon from the atmosphere basically by dissolving CO2 in the raindrops and forming a weak acid. This then weathers the rocks and that reaction ends up creating carbonate ions, which, in turn, are washed into the oceans and waterways. The next change is a bit murky, somewhere along the way the carbonate ions get snaffled up, often it seems by calcium, and then quickly converted into seashells or similar. Eventually the carbon becomes part of the lithosphere as it morphs into carbonate rocks, something akin to the famous white cliffs of Dover perhaps. The carbon cycle is a negative feedback and as such it tends to maintain an existing state. As the sun’s radiation increased and the earth warmed the reaction speed increased, removing CO2 and cooling the planet.

But negative “put it right” feedbacks do not always win. Back in deep time again (2.2 billion & 700million years back) the earth froze over. The trigger is not clear – it may have been something to do with the continents forming. In any event a positive “make it worse” feedback problem developed. The poles froze, the ice reflected more heat, the planet cooled further and froze and cooled some more and once the ice reached the tropics well that was it, a snowball.
http://www.bbc.co.uk/nature/ancient_earth/Snowball_Earth But not forever because – well it isn’t frozen now –and the earth still had at least one get-out-of-gaol-free card left. Volcanoes. Again this took an awful long time but the volcanoes slowly put lots of CO2 and other gases back into the atmosphere, which started the world warming again and as the ice melted under the warming blanket of gasses so the reflectivity of the globe reduced and a little more warmth got through, ice melted, water evaporated, warming increased and we were back in business.

There are several mechanisms that create natural climate variability. They are mainly long term changes triggered by changes to the earth’s orbit (Eccentricity), the tilt of its axis varying (Obliquity) and the wobble of the axis (Precession). These changes are regular and predictable albeit on long time scales. They are called Milankovitch Cycles.
Volcanoes and solar activity also influence the climate and they are not regular or predictable but we can pinpoint those events using tree rings and/or ice cores for proxy dating information and compare the results against historical records of climate events such as the mediaeval warm period. The signature of the Mt Pinatubo volcanic eruption in 1991 is visible as a 2 or 3yr dip in global temperatures but in general global temperatures are rising and CO2 emissions are increasing at a much faster rate than has happened with previous natural climate variation.
Studies of the Ice Ages go back quite a long way and there is now a recognized discipline, Paleoclimatology, thanks to Svente Arrhenius, who in 1895 suggested that a reduction in CO2 concentration in the atmosphere could account for the drop in temperature during the ice age. He was also the first person to investigate the effect that doubling atmospheric carbon dioxide would have on the global climate.
Comparing historical data with the temperature rise over the last 100 or 150 years it seems there is a mismatch, first there is an of excess CO2 in the atmosphere but also the changes are happening much faster than would be expected. http://earthobservatory.nasa.gov/Features/GlobalWarming/page3.php
The only way the models can reflect what actually happened is if the CO2 produced by the industrial revolution is included in the equation.

How right they were!

This is not surprising really because burning coal and oil is really releasing fossilized sunlight back into the atmosphere and the extra heat must go somewhere.

Aerosols, volcanoes and climate change

Volcanic eruptions produce dust and aerosols that act to provide short term cooling, however seems unclear as to whether there is any long term warming effect from the gasses emitted and also the effect of different aerosols and the interactions between them is unclear.

Most aerosols are of natural origin and key groups include sea salt, nitrates, sulfates, organic carbon, black carbon & mineral dust and they often clump together and form complex mixes. Sea salt, dust and volcanic ash are common types of aerosol, only about 10% of aerosols are of anthropogenic origin.

Different aerosols reflect or absorb sunlight depending on their make up. Large volcanic eruptions can cool the earth for a year or more while sulfate aerosols remain in the atmosphere, black carbon deposited on ice or snow can contribute to global warming by altering the albedo (reflectivity) of the planet. It is a complex area and potential impacts are not fully understood. It certainly makes me worry about potential Geoengineering solutions to climate change….

http://earthobservatory.nasa.gov/Features/Aerosols/

Of Ice and Oceans (climate again!)

This week at the Exeter MOOC that looks at ‘Climate Change’ and its complexity we first looked at the impact of global warming on ice sheets, glaciers and sea ice. Understanding how the warming earth disturbs, amplifies or changes the natural processes of glacier calving and ice sheet melting is really critical. We are depending on this when we estimate how fast and how high sea levels will rise in the coming years. If all the ice sheets melt the sea rise would be 65m but of course that will take quite a long time. Even so with many people living at elevations little more the a meter or two above sea level things will get a bit uncomfortable. Understanding how the glaciers behave will also be critical for understanding the fresh water cycles I think, countries in Asia with high populations and huge rivers may well be put under threat because many of the Asian rivers are fed by Himalayan glacial meltwater. We were given web addresses that showed photographic evidence of a massive decrease in the size of the Himalayan glaciers. There were panoramic photographs taken by the British in the 1920s and again in recent years the glaciers have been photographed from the same positions. Side by side (or actually one above the other) they make a sobering comment on the future.
Glacierworks:Everest is definitely worth exploring.
http://explore.glacierworks.org/en#glaciers

Well that was the first half of the week and the second half was just as challenging because we now started to look at the effects of CO2 being absorbed into the ocean. This is quite a complex thing to get your head around as well.
It involves a bit of chemistry but not too much because I could follow most of it (I think) and chemistry was never my strong point. It works like this … the CO2 dissolves in the sea water and forms a weak acid which then dissociates into free H (hydrogen) ions and carbonates. The carbonates would normally be available to be combined with calcium and used to form the shells of the tiny sea creatures at the bottom of the food chain, but if the environment is made more acidic by an excessive amount of free hydrogen ions the process starts to fail. The acidity in the ocean starts to damage the shells of the tiny phytoplankton and pteropods that form the basis of the ocean food chain and it also makes it much harder for their shells to form. I think of this as being similar to plant sensitivity to soil ph, for example many vegetables can only access nutrients within a certain ph range and we can test our soils and adjust them if necessary. Pity we can’t do that with the ocean.
This ocean acidification is one big long term threat to the ocean food chain and all the people that depend on reefs, estuaries, lakes and inlets, fishing and aquaculture for much of their protein, sport and relaxation. We all need to worry.

Fishing in a lake near Bermagui

I also followed up on some work I had come across by a paleo-climate scientist Andrew Glikson, Visiting Fellow at ANU School of Archeology and Anthropology. One thing I found was information on the relationship between the high levels of CO2, increased sea levels and the four large mass extinction events that have occurred in the history of the earth. It seems to me if rising CO2 on a geological timescale (taking aeons to build up) can cause mass extinctions then there is very little hope that the same will not happen with the current rate of CO2 increase in the atmosphere. We urgently need to stop producing the stuff as we power our homes. Old King Coal has got to go.
Andrew Glikson mentions something called “serpentine sequestration” but all I could find on that was a rather heavy paper from Bath Uni which talks of capturing CO2 and reusing some of it in high tech manufacturing of polymers etc. but the paper recognises that the big problems are cost and finding enough space to sequester the CO2 once it has been captured. It seems to be another attempt at using the mind set that created the problem to attempt to solve it.
On the other hand he also speaks of using soil carbon and a world wide effort to sequester carbon in forests and agricultural projects. And of course we must cut our emissions to Zero ASAP.

Climate change report

There are no photos for this item, just a sad realisation that there is so much more we – the concerned public – must do to make sure that the worst predictions outlined in the current IPCC report are not realised. Corporations, politicians and news media are not acting in our best interests by failing to accept the facts and predictions presented in the IPCC report. So here, in part of the summary for policy makers, are some of the things we need to know.

Summary for Policymakers of the Working Group I contribution to the Fifth Assessment Report

Future Global and Regional Climate Change

Continued emissions of greenhouse gases will cause further warming and changes in all components of the climate system. Limiting climate change will require substantial and sustained reductions of greenhouse gas emissions.

The global ocean will continue to warm during the 21st century. Heat will penetrate from the surface to the deep ocean and affect ocean circulation.

It is very likely that the Arctic sea ice cover will continue to shrink and thin and that Northern Hemisphere spring snow cover will decrease during the 21st century as global mean surface temperature rises. Global glacier volume will further decrease.

Global mean sea level will continue to rise during the 21st century. Under all RCP scenarios the rate of sea level rise will very likely exceed that observed during 1971–2010 due to increased ocean warming and increased loss of mass from glaciers and ice sheets.

Sea level rise will not be uniform. By the end of the 21st century, it is very likely that sea level will rise in more than about 95% of the ocean area. About 70% of the coastlines worldwide are projected to experience sea level change within 20% of the global mean sea level change.

Climate change will affect carbon cycle processes in a way that will exacerbate the increase of CO2 in the atmosphere (high confidence). Further uptake of carbon by the ocean will increase ocean acidification.

Cumulative emissions of CO2 largely determine global mean surface warming by the late 21st century and beyond. Most aspects of climate change will persist for many centuries even if emissions of CO2 are stopped. This represents a substantial multi-century climate change commitment created by past, present and future emissions of CO2.

A large fraction of anthropogenic climate change resulting from CO2 emissions is irreversible on a multi-century to millennial time scale, except in the case of a large net removal of CO2 from the atmosphere over a sustained period.

Surface temperatures will remain approximately constant at elevated levels for many centuries after a complete cessation of net anthropogenic CO2 emissions. Due to the long time scales of heat transfer from the ocean surface to depth, ocean warming will continue for centuries. Depending on the scenario, about 15 to 40% of emitted CO2 will remain in the atmosphere longer than 1,000 years.

Sustained mass loss by ice sheets would cause larger sea level rise, and some part of the mass loss might be irreversible. There is high confidence that sustained warming greater than some threshold would lead to the near-complete loss of the Greenland ice sheet over a millennium or more, causing a global mean sea level rise of up to 7 m.

Current estimates indicate that the threshold is greater than about 1°C (low confidence) but less than about 4°C (medium confidence) global mean warming with respect to pre-industrial. Abrupt and irreversible ice loss from a potential instability of marine-based sectors of the Antarctic Ice Sheet in response to climate forcing is possible, but current evidence and understanding is insufficient to make a quantitative assessment.

Methods that aim to deliberately alter the climate system to counter climate change, termed geoengineering, have been proposed. Limited evidence precludes a comprehensive quantitative assessment of both Solar Radiation Management (SRM) and Carbon Dioxide Removal (CDR) and their impact on the climate system.

CDR methods have biogeochemical and technological limitations to their potential on a global scale. There is insufficient knowledge to quantify how much CO2 emissions could be partially offset by CDR on a century timescale.

Modelling indicates that SRM methods, if realizable, have the potential to substantially offset a global temperature rise, but they would also modify the global water cycle, and would not reduce ocean acidification.

If SRM were terminated for any reason, there is high confidence that global surface temperatures would rise very rapidly to values consistent with the greenhouse gas forcing. CDR and SRM methods carry side effects and long-term consequences on a global scale.

Canberra – a well kept secret?

I am sure that Canberra must be Australia’s best kept secret, there are often groaning sounds of boredom when the name is mentioned but I really enjoy it and always find interesting things to do and places to visit.
My most recent visit was a weekend in August, I had arranged it with family members and travelled up the Clyde Mountain road on a Friday afternoon, we met for drinks and dinner that night at The Pot Belly in Belconnen. The Pot Belly is something like a local pub with overtones of an old fashioned jazz cellar and a bistro with live music. It has good food and a great atmosphere, I had fried peppers stuffed with feta cheese coated in a tempura type batter. Really good, mild at first and then a warm chilli taste as you reach the last bite, No photos of this dish (which is a shame because it was served on a bread board) nor of the venue I’m afraid but they do have a Facebook page you can check out.
The next notable event was a visit to Geoscience Australia, the national agency for geoscience and geospatial information. Does this sound boring? Well it isn’t. This establishment opens its doors to the public for one day each year and offers an insight into their work.

Geoscience Australia opened its doors to the public and it was a great success

The open day is really successful, engaging children and awakening their curiosity and their interest in science. However there is also plenty of information and activity interesting and complex enough to engage the enquiring adult as well and the day included several 30 minute talks on diverse subjects covering some of the ways that geoscience is being applied to important challenges such as managing ground water and refining GPS to centimeter accurate positioning. There was a tour of the Tsunami Warning Centre, a tour of the laboratory and something called “Fossil Fun” (bookings essential for this one) and around 35 or 40 displays.

This was a demonstration of how a volcano erupts, it was very popular but the timing was a bit unpredictable

One of the displays included seismic surveys – it had sensors set up outside along the fence line and a pad near an instrument centre housed in a tented enclosure. Children were invited to hit the pad with a mallet and look at the effects on the instruments. I didn’t get to see the instruments or hear exactly what was being revealed below the ground because the display was popular, the queue was long and there were so many other things to see.
The activities aimed at children and families were just brilliant, everything from a “GPS geocache adventure” to an appearance by a TRex dinosaur on the balcony.

T Rex appeared on the balcony with great snapping teeth and a loud roar.

And then it got out

T Rex escaped into the grounds…..

And attacked a visitor. Who said science was boring?

After all this excitement my next Canberra experience was a complete contrast, I went to the Art Gallery with a pre-booked ticket to the Turner From the Tate exhibition, peaceful, calm and colourful this magnificent exhibition was a wonderful counterbalance to the immediacy of the Geoscience experience. I wandered through gallery complete with the hired audio tour which I felt was of limited use although it did draw my attention to one or two things I might otherwise have missed. I have long admired and enjoyed Turner’s work and this exhibition was a joy. Amazingly we were allowed to take photos as long as a flash was not used. Never the less I somehow felt constrained not to photograph the works until I saw the very last watercolour at which point I overcame my reticence and photographed just this one.

An exquisite Turner watercolour.

But my wonderful weekend had not yet ended. Without my being aware of it high tea at the Wedgewood tearoom had been booked so the afternoon ended with Champagne, Earl Grey tea and a selection of delicate sandwiches, savories and sweets served on fine china.
I love Canberra.