President-Elect Trump...

Although not strictly in keeping with the theme of this blog I feel this next post is important. In just 2 weeks the most highly emitting nation in the world is put under command of a climate change sceptic. Now it’s easy to jump on the bandwagon here regarding Donald Trump, however, I will refrain from doing so. What I will endeavour to achieve is rational; balanced post highlighting the problems the progress against climate change may face.

The Paris Agreement of 2015, brings together all nations under a common cause to “undertake ambitious efforts to combat climate change and adapt to its effects”. A moment of great progress in the face of global necessity. Its central aim is to keep global temperature rise below 2degrees and although extremely optimistic, it does provide a necessary first step in a lot of nations in the conversion of national policy with a wider aim. It requires global best efforts to establish appropriate financial flows, a new technology framework and an enhanced capacity building framework. The framework currently has 122 parties ratified of 197 including the UK, US, China, Russia, and India. In the run up to his election, Donald Trump conclusively stated that he would be pulling out of the agreement under the pretence that he believes climate change is a concoction. In November 2016 this changed, he now has an open mind about the policy. However, we must be well aware of his original intentions especially given his leniency to be manipulated by oil and coal embracing states. Similar to the 24 state demand for Trump to kill the centrepiece to Obama’s internal emission plan, the reduction of carbon emissions to 32% below 2005 level by 2030. It is clear that his turbulent stance on climate change could present significant barricades to successfully implementing low-carbon economies global. At least 630 firms in the US with a collective revenue of almost $1.15trillion have used their economic power in the US to urge Trump to reconsider. Only time will tell if the climate change debate will take a hostile turn despite its recent progress in the coming months.

What we can learn from the last glaciation

The major threat of abrupt climate change comes from a combination of the three systems discussed in this blog. The major tool for initiating glaciation is the Arctic Meridional Overturning Circulation, a part of the Thermohaline system. Henry et al (2016) found that increasing CO2 levels coincided with the H-stadial reductions in AMOC. This warming then caused the discharge of major icebergs from the Greenland Ice Sheet and a melt in sea which kick-started the cooling the disruption of salinity and temperature in the surface waters of the Arctic. Therefore, inhibiting the circulation and causing global cooling. This extreme swing pattern is not a new concept, James Lovelock’s early ‘Gaia hypothesis’ stipulated that the more extreme we force the global system the more extreme the reaction will be in order to eliminate the forcing. In that case either rapid heating to cause total melt or an onset of glaciation, the latter being the more scientifically sound.

Schmittner characterises the whole process as general warming and cooling in the North Atlantic and the opposite in Antarctica. This characterisation is consistent with disruptions to the interhemispheric heat transport of the thermohaline system. As previously mentioned, warming in the Arctic trigger the cooling through melting of ice causing massive freshwater influxes. Recent evidence reinforces this using deep sea sediment ratios. It transpires that when around a 2degree C differential arises between the North Atlantic and the sub-tropical North Atlantic it corresponds with a sever slowing or even collapse of the AMOC.

What is the likelihood of this happening to us?

Using 4 climate scenarios devised by the IPPCC in their 5^th Assessment Report, Cheng et al (2013) assessed the likelihood of the RCP scenarios causing changes within the AMOC. RCP4.5 assumes an emissions peak of 2040, this is the most conservative estimate given the changing tide of consumers in Asia and an unwillingness to cut emissions in the US. Using this scenario by the year 2100 the AMOC will see a projected weakening of 5-40%, this rises to 15-60% in the RCP8.5 scenarios which assumes continuous rise throughout the 21^st Century. Although most likely an extreme case the RCP8.5 scenario shows that a significant weakening of the system is feasible within the 21^st Century which will incite massive regional climate changes a pose new unplanned problems for the world population. The more conservative RCP4.5 shows a stabilising of the AMOC in the latter half of the 21^st century, however a 40% weakening is still significant enough to bring about noticeable shifts in regional climates, so much so it may generate new climate challenges in new locations such as flooding a drought, or exacerbate those already plaguing the global population. 5-40% is a significant ranger considering the consequences however it does provide a confirmation window for Schneider et al (2007) and Cheng et al (2013) who predicted 25-30% weakening by 2100 and 21% (RCP4.5) and 36% (RCP8.5) which are much more precise observations. Furthermore, Cheng et al concluded through multimodel assessment that North Atlantic SST variability in the late-19^th to early-20^th century is consistent with external forcing implementing aerosol forcing as the main driver of AMOC shifts. This is not to say that CO2 may not result in a similar fate as can be seen from this blog alone a number of academics all agree that the forcing is present and a pressing concern the only ambiguity lies in by how much the AMOC will weaken.

Is Geoengineering a Solution? A review of Cvijanovic et al, 2015.

The most likely tipping point and if not at least the most significant positive feedback mechanism in the Arctic system is the albedo feedback of sea ice. This article bypasses the assessment of feasibility and methodology and look at if we could whiten large areas of the Arctic Ocean, could we in fact counter this feedback loop and cause polar cooling.

The study utilises the CSEM global coupled climate model incorporating atmosphere, land, ocean, and sea ice models. The newer CESM model results in better representation of the meridional overturning circulation and sea surface temperature, in comparison to the CCSM3 model.

The method would operate by increasing surface albedo which would result in high latitude surface budget alterations and surface cooling which would spread aloft and southward. This method opposes the geoengineering projects that propose to block incoming radiation with injecting sulphates in to the stratosphere, as this aims to alter the total energy budget via the incoming radiation. Caldeira and Wood, 2008 and Tilmes et al, 2014 modelled these scenarios with reasonable success, although Tilmes concluded that currently the amount of aerosol needed to dim the Arctic is unrealistic and would most likely be blown to lower latitudes anyway so it instead would require extremely large reflects positioned in space above the pole.

The Important Part

The imposition of ocean albedo alterations in the Arctic resulted in the desired recovery of sea ice and decreased warming, with a trend or recovery over the first two decades and no discernible trend beyond. Its success operates with an efficiency peaking at 76% when albedo is enforced over 75-90 degrees North, lower than that proves ineffective in causing ice to recover as it is too far South, 80-90degrees also fails as the coverage of ice is already rather covered therefore little room to alter albedo.

Its success stabilises the ice cover at around 40% of the preindustrial value, which for context, is 37% higher than should nothing be done at all in the case of a 4xC02 climate with about 10degreesC in the Arctic. However, even the most extreme cases of the model have only a modest impact on sea surface temperatures and permafrost.

What this reinforces is that sea ice is a self-supporting system as this one feedback mechanism can cause sea ice to reform and stabilise. It also states that the effects of this reclaiming of sea ice effects the mid-latitudes and the precipitation pattern experienced there.

In essence then, this report serves to highlight that sea ice, although effecting precipitation patterns in the mid-latitudes is actually rather insignificant in terms of its ability to incite a change within the climate system.

Figure 1: "Annual surface air temperature anomalies (K) between 30° and 90°N in modified ocean albedo simulations relative to the control 4xCO2 simulation. Dashed areas indicate the anomalies that are statistically significant at the 95% confidence level. In addition to the Arctic cooling, altered albedo simulations also show notable warming off the West Coast of North America (less pronounced in alb70–80N but still present). This pattern of temperature response is found in all simulations with imposed albedo modifications. Thin and thick contour lines indicate the areas with annual mean sea ice fractions larger than 15% and 80%, respectively." (pg. 5). Credit: Cvijanovic et al 2015

On a Wider Note

The IPCC seems to think geoengineering is vital to restrain global warming, specifically carbon capture, so much so that the U.S. Department of Agriculture guaranteed a loan of $91million to build a carbon capture facility in Louisiana. However, it is most likely not enough to halt global warming. At best projects that block incoming radiation are a plaster that needs regularly refreshing in order to block further degradation while we find a solution to reduce the massive amounts of CO2 filling the atmosphere. CO2 removal from the atmosphere sets a dangerous precedent for producing CO2 I the first place and could just end up playing a continuous game of catch-up. The only real solution is to overhaul the global system and ‘turn the tap off’ instead of trying to widen the plug.

Consequences of a Melting Greenland Ice Sheet

At its extremity a complete melt would cause a global sea level rise of about 6 metres, although this pales in comparison to the 60 metre rise we would be faced with should Antarctica melt, however unlikely. However, we’ll ignore that part and focus on the Greenland Ice Sheet. 54% of Asia’s urban population resides in low-lying coastal areas (Kumar, 2013), according to geohive.com that stands at a population of over 2.1 billion people. This means that in Asia alone over 1 billion people are at risk of rising sea levels.

Figure 1: Visualisation of the cumulative melt days observed on the Greenland Ice Sheet. Credit: NSIDC

Let’s Look at the Melt, and when will it affect us?

Importantly, the rate of melt is increasing. In fact, between 2002 and 2009 the rate of ice loss more than doubled from 137gigatonnes/year to 286 gigatonnes/year. This halves the lifetime of the sheet. Rather obviously though, Greenland strength is the cooling caused by its immense size, as it shrinks it loses its source of cooling therefore melts quicker. Now that our CO2 levels have increased above 400ppm permanently it is expected that the ice sheet will lose 20 to 41% of it volume over the next 400 years (Stone, 2010), equivalent to roughly 1.4-2.8 m sea level rise. Despite the ARR noting that process we’d expect to see over millennia are occurring on a decadal basis the threat from the Greenland Ice sheet is a long-term one. Short-term effects are negligible, and although that can give us comfort we are continually accelerating that melt.

Consequently, we’ve got time. Not to say that should affect the urgency of climate awareness and action but at least in this regard we can start the planet on a path that will halt this melt process.

Consequences of Arctic Sea Ice Melt

Although a perennially ice free Arctic Ocean may be decades away, an ice free summer is a much more pressing reality. Fundamentally, this means the temperature increase is so that it melts all of the seasonal ice annually and consequently starts to erode down the solid multi-year ice. This point will almost undeniably occur within our lifetime and maybe sooner than we think. Basic extrapolation of sea ice volume data places it in roughly 2020. Given, the simplicity of this prediction it would be foolish to take it as truth, however, Overland and Wang (2007, 2009, 2012) used climate model projections as well as encompassing several more severe drops such as 2007 and 2012. Climate models using CMIP5 are often cited as being too conservative (Kumar et al, 2013), yet they still predict a sea ice free summer by around 2040. Considering this is considered a conservative estimate it may well be closer towards the models that assimilate rapid changes which predict around 2030.

2030? Is that our best guess? Holland et al (2006) would agree. Despite it being 11 years later the paper predicts several rapid ice extent retreats, each one 4 times larger than observed decline. Incidentally this would be an underestimate, both the 2007 and 2012 minima were far lower than was predicted (NSIDC), this makes his estimate of 2040 using 7 different climate models arguable conservative.

Figure 1: Sea Ice extent in September 2015. The gold line represents the 1981-2010 average September extent. Credit: NASA

So what if we have ice-free summers by 2030?

Departing from the physical and environmental consequences let’s look at the anthropogenic impacts. By this, I refer to both the Inuit populations whose livelihoods rely on the formation of the sea ice, but also to the market and how this new scenario we have created can be exploited.

Tourism to the region has already increased over the past decades with more of the Arctic ocean becoming more and more accessible to cruise ships for longer times within the summer. Adventure Canada have run tours to the Arctic for 25 years and operate as sustainably as possible, including engaging with locals through employment and meetings to not impose on their culture however a new wave of tourist industries may not carry out the same procedures. Referring back to environmentalism, the burning of diesel produces non-organic black carbon, as opposed to that produced by forest fires which can bring about cooling this form does the opposite. Shipping contributed to 7-9% of global black carbon (http://www.theicct.org/blogs/staff/black-carbon-emissions-shipping-fact-checking-conventional-wisdom) and given that it accounts for 90% of international trade (International Chamber of Shipping, 2014) it is an acceptable level. However, in the Arctic unfortunately the same cannot be said. Localised production of black carbon by increasing levels of cruise ships and oil seeking ships, read on, causes a layer of black to form on top of the remaining ice within the area. Thinking back to the albedo effect, this new dark surface causes increased shortwave radiation absorption directly into the ice, promoting melt.

Despite Shell announcing in September 2015 that it would be abandoning exploration in Alaska for the foreseeable future, it is not likely to last for long, certainly not for the rest of the field. Unfortunately, with dwindling land and ocean supplies of oil the Arctic is the next suspected area for exploration. Despite difficulties faced by Kulluk in 2012, ran aground after losing its tow in the heavy weather, there is almost certainty that companies will move back in the coming summers as it becomes safer and safer to explore during the summer months. This brings with it the dangers of oil spills among other incidents, all of which would be catastrophic in such an environment.

Figure 2: The Kulluk Oil Drill Barge run aground in Northern Canada after it became detached from its tow line in stormy seas. Credit: United States Coastguard

A quick cultural run down.

The loss of Arctic Sea Ice and it's subsequent effects on wildlife habitats, numbers, and migratory behaviour; the transport routes needed to subsist; the duration of seasons; and the condition of fisheries and wild marine life are vital to the survival of native populations. The Arctic Resilience Report released in 2016 states that the mobility of the populations and their animals is already greatly reduced therefore causing a massive change in the ecosystem structure within the polar regions. The increased tourism may also reduce the sense of place felt by natives as well as the effects of a dominant and disruptive body of tourists entering their social system.

Arctic Resilience Report, Briefly.

Newspapers today have embraced the concept of a tipping point almost entirely. Whether that be because ‘slow gradual decline’ doesn’t quite have the same grip as ‘beginning of downward doom spiral’ or whether it be as a result of the Arctic Council. The Independent, The Guardian, The Daily Mail. All major newspapers and all spreading the word that we have passed or are rapidly approaching a tipping point in the Arctic. However, many scientists disagree. It is a contested topic however the Arctic Council seem pretty conclusive in its 2016 Arctic Resilience Report. Being made up of the 8 Arctic nations it provides an academic balance of researchers in addressing 19 of the current threatening 'regime shifts' including that of the Arctic Sea Ice, Thermohaline System and the Greenland Ice Sheet. Conclusively however, they state they exist, and that these regime shifts are not catastrophic. In terms of Arctic Sea Ice, Zhang and Walsh (2006) propose that there are counter-mechanisms that will halt a further regime shift beyond ice-free summers. A note of concern is that the report states that changes in the Greenland Ice Sheet that were thought of as being millennial shifts are occurring on a decadal scale. Due to the size of the sheet no immediate threat is posed, yet we should take note at the severity of the forcing is a result of anthropogenic influence.

The Polar Vortex?

Our understanding of Arctic Sea ice is forever incomplete. The extreme interconnectedness of the global system means that despite decades of research we are forever furthering our understanding. a recent example of this comes courtesy of David Barber, a Canadian scientist. In a TED Talk last year he presented the early basic ideas of the concept, alongside a good overall summary of the problems facing sea ice.  It is only now though that this new concept is of concern, a recent article in Nature Climate Change suggested that this year we could feel the effects of a weakening polar vortex significantly. Previously it has been linked to cooling in the Pacific mid west (2012), however, this Winter as a result of the continual weakening as a result of global warming melt sea ice its effects could be felt across Europe and Asia.

Figure 1: An animation depicting the traditional polar vortex. Credit: Washington Post

A strong polar vortex holds the cold air into the Arctic decreasing the air temperature in the Arctic and allowing for warmer temperatures further South, as visible in Figure 1. The now more unstable vortex is unable to function as it has done previously, as a result we in the UK, as well as North America, Northern Europe and Asia, could experience severe cooling in February. Although this may be inconvenient it isn't the end of the world. This would set a new precedent for the anomalies as previously it has only affected Northern USA.

Figure 2: The adjusted, weaker polar vortex sinking over the USA causing cooling through the US. Credit: Washington Post

The more significant impact can be found in the Arctic. This loss of cooler air will most likely contribute to a warmer surface air temperature in the Arctic. Although this is still a recent topic of inquiry so it is unsure as to how it will effect the Arctic this winter we can predict that it will maintain the seriously low rate of ice formation that has been so prevalent this winter. Due to the lack of research it is unclear how the polar vortex will shift however there is no suggestion of a tipping point instead the vortex has weakened steadily over time, however, the effects have onset rather immediately.