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COP21 Paris 2015

2015-12-04T12:04:57Z

Marc Height:

[http://www.designingbuildings.co.uk/wiki/Climate_change_science Read Marc Height's article on climate change science here.]

= Introduction =

In December 2015, representatives of world governments have convened in Paris to debate the fine details around a deal on climate to succeed the Kyoto Protocol – which is due expire in 2020.

Diplomats and heads of states are convening for the 21st Conference of Parties, or COP21, the latest in a line of United Nations meetings on climate change action – that is, how to mitigate the effects of future climatic changes, and how to adapt to changes that are already underway. Within the wide range of discussions two key things are deliberated:

* The ambition and pace of emission reductions.
* The level of financial help pledged to vulnerable nations to adapt to climatic changes and invest in clean energy.

= A history of Parties =

The United Nations Framework Convention on Climate Change (UNFCCC) is a treaty that was set up at what is known as the Earth Summit – the United Nations Conference on Environment and Development – in Rio de Janeiro in 1992.

The treaty itself doesn’t set any specifics around addressing emissions. It has an aim of ‘stabilising greenhouse gas concentrations in the atmosphere’ to prevent dangerous climate change, but is in essence a framework under which countries can get together to thrash out legally binding protocols on cutting greenhouse gases. The UNFCCC in itself is non-binding, but states that parties should act to protect the climate system through ‘common but differentiated responsibilities’, with developed countries – or, in the main, ‘Annex 1’ countries – taking the lead.

A total of 196 Parties, or countries, make up the UNFCCC, and these Parties have met annually since 1995 when the first Conference of Parties, or COP1, was held in Berlin. The COP meetings are a forum where Parties get together to work out how to achieve the aims of the UNFCCC treaty.

COP meetings have been turbulent. COP3 in Kyoto, 1997, as the location might suggest, gave birth to the Kyoto Protocol. The Protocol was formed after the Parties decided at COP1 that it was not adequate for Annex 1 parties to just stabilise their emissions at 1990 levels by the year 2000 (which was the initial aim of the UNFCCC).

The Kyoto Protocol set varying binding emission reduction targets for Annex 1 countries. It finally came into force in 2005, and its first round ran to 2012. The Protocol had an overall aim of reaching a combined 5% cut in emissions from 1990 levels by 2012 across the Annex 1 bloc. Countries were free to decide how to reach their targets – be it by increasing forest cover, as well as funding emission reduction efforts in other countries; alongside making direct cuts to their own emissions.

In terms of a mechanism to reduce emissions, Kyoto is seen by many as a failure. The delay in it becoming international law saw emissions rise unchecked in the interim, and while some Parties, like the European Union, reached their eventual goals, others did not. The Protocol was famously not ratified by the US – at the time the largest and currently the world’s second largest emitter. And the focus on developed countries, along with the US drop out, meant that global emissions over the first commitment period soared – particularly from China.

The second Kyoto Protocol commitment period runs from 2012 to 2020, and does not include all the Parties that took part in the first period. Japan and Russia, among others, said they would not take on further Kyoto targets and Canada received a great deal of criticism when it dropped out of the process altogether in 2011.

Deliberating on a follow up to Kyoto is exactly what COP21 is all about, but what have been the other key COP milestones over the past few years, and why has it taken this long to find Kyoto’s successor?

= Recent COP landmarks =

=== COP13 ===

COP13 in Bali, 2007, culminated in the ‘Bali Road Map’ which set its sights post-2012. A big part of the roadmap was the ‘Bali Action Plan’, which would set a course for the following two years towards the last big purported chance to get a global deal on climate – COP15 in Copenhagen in 2009.

=== COP14 ===

COP14 in Poznan, Poland, 2008 made some progress on funds for adaptation and committed to achieving a global deal the following year in 2009.

=== COP15 ===

Then came the infamous COP15 in Copenhagen in 2009.Talks broke down and the conference was hailed as a failure by many observers. Channel 4’s Jon Snow called it the most distressing reporting experience of his career.

The US President Barack Obama was struggling to get an emissions trading bill through the US senate at the time, and pre-negotiations between the US and what had by then (just) become the world’s biggest emitter, China, did not amount to much. The Chinese President Wen Jiabao reportedly left the conference halfway thorough and sent an official to negotiate with Obama. The process itself descended into chaos, with world leaders stepping in to write some parts of the final text themselves.

The Copenhagen ‘Accord’ didn’t stack up to much. It was not legally binding and didn’t contain any binding commitments for emissions reduction. It acknowledged the severity of the challenge of climate change, and expressed a ‘strong political will’ to combat it, and make ‘deep’ cuts to emissions.

However, on climate finance, COP15 set up a target for developed countries to generate $100bn a year by 2020 in aid for developing countries to deal with the effects of climate change – a key part of negotiations today. It also set up a mechanism to transfer technology to developing countries.

=== COP16 ===

COP16 took place in Cancun, Mexico in 2010 and ended up with measures from the Copenhagen Accord formalised in the ‘Cancun Agreements’ – the main headline being that Parties agreed for the first time to maintain global temperature increases to below 2°C. Again there was no legal framework here. The commitment to $100bn in finance transfer was finalised.

=== COP17 ===

Over to Durban, South Africa in 2011 for COP17, where the ‘Durban Platform for Enhanced Action’ was created.

This significant platform set in motion the framework for the next few years and also began the hype behind COP21 – under the Durban Platform Parties agreed to seek a universal legally binding agreement on climate change by no later than 2015. This would come into force by 2020 and would succeed Kyoto. The Durban text reiterates the 2°C target and provides an option to increase ambition to limit the temperature rise to 1.5°C.

=== COP19 ===

After a lacklustre COP18 in Doha, COP19 in 2013 in Warsaw, Poland was more interesting. It aimed to set a timeline to facilitate an agreement in COP21, create a mechanism for a new ‘loss and damage’ framework (how to enhance knowledge, action and support for developing countries affected by extreme events), and progress the provision of long-term finance.

On the first point, the now well-known ‘intended nationally determined contributions’ (INDCs) – the eventual vehicle under which Parties would submit their pledges on emissions action for COP21 – were discussed. This marked a key moment for COP21. A mechanism was decided in which countries would take a ‘bottom-up’ approach in setting their own targets to reduce emissions, fundamentally different to the top-down approach of Kyoto.

=== COP20 ===

In 2014, COP20 was held in Lima, Peru. Work began on the draft agreement text for COP21 (which would subsequently be worked on at interim meetings for negotiators in Geneva and Bonn), and the process for Parties to submit INDCs was finalised. It was decided that INDCs would focus on mitigation (emissions reduction) – and include detail on base years, time frames, scope, methodologies, and whether the effort was fair.

Some progress was made on other areas, including a boost on climate finance (though developing countries were disappointed with the lack of progress on long-term finance) and loss and damage.

In summary, in terms of coming up with a successor to Kyoto, COP15 didn’t deliver, and subsequent COP meetings, particularly COP17 in Durban, set sights on Paris as the next big chance to get a truly global, legally binding agreement on reducing emissions. That’s why COP21 is important.

= COP21 – from top-down to bottom-up =

A lot of work has been undertaken since Lima in interim negotiations taking place in Geneva and Bonn.

The draft negotiating text for Paris at the start of the year weighed in at a hefty 86 pages, with a lot of work required between February’s Geneva meeting through the three subsequent meetings in Bonn to get it down to something more manageable.

A lot of streamlining work has been done to try and whittle the text down into something shorter. The last official interim meeting in Bonn towards the end of October resulted in a final negotiating text for COP21 of 51 pages. This text however still had a large amount of interpretation in the form of square brackets [representing wording yet to be decided]. There is much left to be honed in Paris.

Some of the key areas of the text concern mitigation ambition, finance, and how ambition outlined in emissions pledges, in the form of INDCs, can be ratcheted up after the meeting.

Regarding the latter, INDCs mark the key difference between any agreement formed from COP21 and the Kyoto Protocol. This time round Parties themselves are forming the level of ambition, outlining what they are prepared to do in their INDCs, rather than it being imposed on them. While some have criticised the ‘potluck’ aspect of whether INDCs will add up to anything meaningful, they exist so countries can be more prepared for the talks and to make a binding treaty more likely.

Individual INDCs can be viewed on theUNFCCC website, but what do they add up to? Asynthesis reportfrom the UN says that the combined pledges will result in 2.7°C of warming on pre-industrial levels by 2100. While this is above the 2°C target, it is a marked improvement from business as usual, and many commentators have made this point.

But it does point to an ‘emissions gap’ to reach 2°C, with the United Nations Environment Programme (UNEP) estimating that to reach the target, around 12 to 14 gigatonnes more carbon dioxide needs to be saved by 2030. TheUNEP reportrecommends early action on emissions to keep costs low and avoid deeper and more challenging cuts later on.

There is already an acknowledgement that post-Paris, countries will need to look to increase their ambitions to close the gap, possibly doing so every five years. This is part of the negotiating text.

= Finance =

One of the more contentious issues around any form of deal to come out of Paris is to do with the level and flow of finance from developed to developing countries to help mitigate and adapt to a changing climate, as well as compensate for loss and damage due to climate events. Indeed, some INDCs from developing Parties state that action is conditional on the provision of climate finance.

The COP16 commitment from richer nations to provide $100bn annually to developing countries by 2020 will form one of the key battlegrounds for negotiators. Developing countries are looking for more certainty around this promise. South Africa’s Nozipho Mxakato-Diseko, who represents the G77 and China (now a total of 134 developing nations), told a press conference at the final Bonn session that: “Whether Paris succeeds or not will be dependent on what we have as part of the core agreement on finance.” The group wants an agreement for aid to be scaled up from a floor of $100bn in 2020.

On the other side, developed countries would like to broaden the definition of a donor as not just an Annex 1 country, but all countries that are in a position to donate. The G77 group wants to keep the Annex segregation.

How ‘differentiated responsibilities’, as described in the original UNFCCC treaty, are seen by developed and developing countries – in terms of a simple split of the world into Annex 1 and 2 countries as was the case in 1992, versus a more general sharing of obligations – is key to negotiations.

A recent OECD report says that a level of $64bn of finance was reached in 2014, though there is reportedly distrust from some of the negotiators around this figure which highlights some of the entrenched dividing lines that still exist in these negotiations.

= The need for action =

Speaking in late September in London, Al Gore, climate change guru and self-proclaimed ‘former next President of the United States’, framed the context for COP21 in three questions.

He asked, ‘must we change?’

Offering some fundamentals on climate change science and examples of erratic weather events we are exposed to (‘Every day the news is like a nature hike through the Book of Revelation’); his answer was a resounding ‘yes’.

He then asked,’ can we change?’

Focusing on the increasing proliferation of renewable energy technologies, game-changing improvements in cost and rapid innovation means that we are close to renewables being cheaper than the incumbent energy regime. ‘Of course we can change’, Gore proclaimed.

The last question is what Paris really comes down to. ‘Will we change?’

Gore was optimistic that this time there would be some form of global agreement, due to the bottom-up and inclusive nature of the pre-COP21 INDC process.

It is not just environmentalists and climate activists that are in favour of a strong deal in Paris. Many in the business community are pushing for a global framework and solution to the climate crisis. Forward-looking businesses are aware of the risks they are exposed to from climate change – the Confederation of British Industry (CBI) has put a figure on the value at risk from climate change at £4.5tn.

= What might happen in Paris? =

The format of COP21 will see world leaders arrive for the first few days of the conference – including Presidents Obama and Xi Jinping. The draft agreement will be worked on in the first week, then, ideally when largely complete, handed over to high-level negotiators, supported by a senior minister acting as COP President, where negotiations will continue behind closed doors. A final plenary meeting at the end of the process could result in a deal – but there is need for consensus so in theory any country could act to veto it.

Some commentators, speaking at a recent conference under Chatham House rules, have criticised the final negotiating text that will be taken into COP21. One described the process of turning the messy document that came out of Lima into a legible and comprehensive document for Paris as a ‘failure’, and added that what is left is a confusing text that is incomprehensible – even to experienced lawyers. This ‘far from ideal’ document means ministers will have their work cut out for them, they said.

Any agreement will certainly not include a global price on carbon (which the business community is crying out for), Christiana Figueres, Executive Secretary of the UNFCCC, has said. It is also unlikely to include any progress on banning fossil fuel subsidies.

But there is much to be optimistic about. Compared to the turbulent exchanges from 2009 between the US and China, this time, and in advance, the two countries have agreed work together on addressing climate change. And both the US and China are taking real domestic action on emissions.

Further afield, Australia and Canada have ousted their old climate-sceptic leaders and now have governments more likely to progress action on this issue. The G7 has agreed to decarbonise by the end of the century.

There is broad speculation that, due to the bottom-up nature, COP21 will result in some form of meaningful agreement. But any decided action must be acted upon quickly – the science says we may already be locked into a 1.5°C temperature rise, and some small island states have argued this is the absolute upper level that we should be aiming for.

Perhaps making real headway on addressing climate will be more a story more from the private sector. An agreed framework could give businesses the confidence they need to make the carbon cuts they say they can make. It could also be a story of technology – we are seeing renewables expand at a phenomenal rate. The growth of and reduction in cost of solar power, for instance, has taken everyone by surprise. And the indigenisation of these technologies could help developing countries grow economically.

Paris needs to come up with the goods if we are to avoid the risk of irreversible climate change – heat waves, crop failure and sea level rise, among other impacts. But obviously COP21 does not mark the end of road – it is just another step, and there will be a lot of work to do afterwards. The deal needs to be one that can renew itself.

The Met Office recently announced we are to hit an average 1°C rise on pre-industrial temperatures this year – halfway to the 2°C limit. The passing of this crucial milestone, with further temperature rises locked in and a shrinking carbon budget, offers some sobering context as diplomats sit down in France.

We’ll soon know the path we decided to take.

-----
This article was written by--[[User:Marc Height|Marc Height]] 12:04, 04 Dec 2015 (BST)

First published in the November 2015 issue of [https://www.energyinst.org/information-centre/ei-publications/energy-world/energy-world-november-2015 Energy World].

= Find out more =

=== Related articles on Designing Buildings Wiki ===

* Albedo.
* Biomass.
* Carbon plan.
* Climate Change Act.
* Climate change science.
* Emission rates.
* Energy targets.
* Environmental policy.
* Globe temperature.
* Green Deal.
* Greenhouse gases.
* Intergovernmental Panel on Climate Change IPCC.
* Kyoto Protocol.
* Radiation.
* Sustainability.

=== External references ===

* LinkedIn – [https://www.linkedin.com/pulse/cop21-securing-global-deal-climate-all-eyes-paris-marc-height COP21]

[[Category:International]] [[Category:Organisations]] [[Category:Research_/_Innovation]] [[Category:Policy]] [[Category:Sustainability]] [[Category:News]]

Climate change science

2015-12-04T11:13:00Z

Marc Height:

= Introduction =

Climate change is a particularly difficult problem for humankind to deal with. There are three aspects to the phenomenon that make it so.

First, to mitigate the effects of climate change means taking action now to avoid potentially catastrophic impacts that would take place far in the future – certainly far enough away to be beyond the political, economic and behavioural timescales our society is geared toward.

Second, should these impacts come to pass, it would mean that our mitigation efforts were lacking and at that point it would be too late to do anything about them. The inertia of the earth’s oceanic, atmospheric, cryospheric, biological and chemical systems mean that once ‘dangerous’ climate change is underway, there is not much we can do about it.

Third, these two truths are peppered with a degree of uncertainty around the timing and severity of the changes we may be exposed to. This is all to do with the earth’s ‘climate sensitivity’ – how it, as a system, will respond to the various forces it is being subjected to.

Despite some uncertainty around the severity of the temperature response to a given injection of carbon dioxide, and other greenhouse gases, into the atmosphere, the consensus is:

* That the earth’s climate has always changed over timescales ranging from thousands of years to millennia; that alongside natural forcings.
* Greenhouse gases from human activity are warming the world.
* Effort is needed to reduce emissions and to adapt to the changes that are due to occur from the gases already injected into the atmosphere.

= Climate science =

There are a variety of forces, either internal or external to the earth system, that can have an impact on the climate – that is, the prevailing weather conditions in an area over a time period of around 30 years.

The climate clearly differs depending on the location on the earth’s surface and is in part a result of the redistribution of solar radiation from the equator towards the poles.

Climate is not a static entity. While weather might differ from day-to-day and year-to-year, the climate of a particular area will change over longer timescales. Evidence for this can be found in a variety of places – records of temperature, rain and wind data, for example.

When researchers are interested in finding out about the climate further back than is described in written records, proxy methods can be used to infer climatic conditions.

Tree rings (dendrochronology) can beused to provide a yearly record (one new ring per year) of what the climate was like in a particular area (wider rings indicate warmer years).

Pollen found in soil strata can indicate what sort of vegetation was around in a particular period, and by implication the conditions that allowed this vegetation to grow.

Gas levels in ice cores can give an indication of atmospheric composition, also referenced by year (new ice layers form year after year when snow and ice accumulates at the centre of ice sheets). There are many more methods.

Such proxies have allowed researchers to map the historic climate and how this has varied over different timescales.

A rhythm of climate change is set by the earth’s orbit around the sun. Milankovitch cycles, named after Milutin Milankovitch, a Serbian astronomer and mathematician who is credited with quantifying the phenomenon, relate to the earth’s movement around the sun in space. The tilt of the earth varies over time as well as the extent to which it wobbles on its axis. More fundamentally, the shape of the orbit (eccentricity) changes over time – from being more circular to more elliptical.

These orbital changes affect the amount of solar radiation reaching the earth and set the pace of glacial and interglacial periods in the earth’s climatic history to a 100,000-year timescale. The earth has gone from periods of being ice-free (interglacials) to being extensively covered by ice (glacials), and it is thought that these orbital changes act to kick off the changes between these two states.

These very long-term pulses have on top of them shorter-term fluctuations that affect the climate on shorter timescales and are related to other phenomenon. Currently the earth is in a relatively stable climatic period known as the Holocene which began 12,000 years ago – part of the current interglacial. But other natural factors have had an influence on the climate over this period.

The balance of radiation at and around the earth’s surface can be affected by forces either outside or inside the earth system.

=== Sunspots ===

Externally, the level of solar output varies due to sunspots, for example, and this will affect the amount of outgoing shortwave radiation that makes its way from the sun to the earth.

=== Volcanoes ===

Volcanic eruptions are one classic example, this time the result of the geological system, of an internal force affecting the amount of radiation reaching the earth’s surface. The earth’s radiation balance is affected by the composition of chemicals and particles volcanoes spew into the atmosphere. Global temperatures will drop by up to half a degree for a few years after a big eruption due to sulphate aerosols reflecting a greater amount of the earth’s radiation back to space. Volcanoes also emit greenhouse gases, but at a much lower level than the contribution made by human activity.

=== Clouds ===

Clouds also have an impact on the earth’s surface radiation balance. As well as reflecting shortwave radiation from the sun, they have the effect of absorbing and re-emitting long wave radiation from the earth’s surface. It is thought that clouds have an overall net cooling effect, but how this will change in the future with changes in atmospheric water vapour content, and changes in cloud amount and distribution, is a complex issue.

= Greenhouse gases =

Despite orbiting at twice the distance from the sun than its neighbour Mercury, Venus has a much higher average surface temperature – because it has an atmosphere; one that is largely made up of carbon dioxide.

Venus is an example of a planet that has undergone runaway global warming. While the temperature on Mercury reaches 426°C on its sunward side but falls to -173°C in the shadows, Venus stays at 462°C no matter the location. Venus’ atmospheric carbon dioxide absorbs and re-emits the long-wave radiation from the planet’s surface, preventing it from escaping into space and so warming the atmosphere.

Theory around the atmospheric greenhouse effect has been around since the 1800s. The work of Joseph Fourier in 1824 and then John Tyndall in 1864 helped to first show that the earth’s atmosphere acts to trap long-wave radiation and thus warm the planet, and that there are some gases that are more effective at doing this than others.

The Swedish physicist Svante Arrhenius later used observations of infrared absorption to estimate the effects of lowering the level of carbon dioxide in the earth’s atmosphere. He estimated that halving the atmospheric composition of carbon dioxide would not prompt the onset of an ice age, but, importantly, that doubling atmospheric carbon dioxide levels would warm the planet by a total of 5-6°C. This estimate is within the range of warming predicted by modern day climate models.

Humankind is currently putting these theories to the test, by conducting a planet-wide experiment in which greenhouse gas is injected into the atmosphere in ever increasing quantities.

Today 110m tonnes of carbon dioxide enter the atmosphere every 24 hours as a result of human activities. The concentration of carbon dioxide in the atmosphere hit 400 parts per million (ppm) earlier this year, and continues on its upward trend. This concentration has increased from around 280 ppm before the industrial revolution. Some have argued that we actually needed to reduce this level to below 350 ppm to avoid irreversible and catastrophic climate change.

Though it is the most ubiquitous greenhouse gas related to human activities, carbon dioxide is not the only one. Methane is far more potent, alongside nitrous oxide, CFCs and even water vapour.

These gases are compared to carbon dioxide by their global warming potential (GWP), with carbon dioxide having a GWP of 1. Over 20 years in the atmosphere methane has a GWP of 86, and over 100 years 34 (the time horizon has an effect on the potency of the gas relative to carbon dioxide). CFCs are also very potent greenhouse gases, but are released into the atmosphere in relatively small amounts compared to carbon dioxide and methane.

Focusing on carbon, the natural carbon cycle sees the element move around the earth in various states as a result of natural processes. Levels of carbon dioxide in the atmosphere vary over the year as the earth’s flora ‘breathes in and out’ over growth and decay cycles. However, humans are taking carbon that has long been locked away, out of the system, and are converting it into carbon dioxide at a rate that the earth has never seen before – to levels not seen in the last million years.

[[File:Climatechange1.png|link=File:Climatechange1.png]]

Observed temperature change across the earth’s surface from 1901 to 2012. (Source: IPCC)

We have a climate system that responds to a host of natural, and now also anthropogenic forces. Both sides will have an influence on future climate.

= Anthropogenic effects =

Early indications of anthropogenic effects have already been seen. Fourteen of the last fifteen years broke world temperature records. After what some described as a ‘pause’ in the rate of surface temperature warming (studies have shown the world’s oceans absorbed more heat over the period), 2014 was crowned the warmest year on record by the US National Oceanic and Atmospheric Administration. The Intergovernmental Panel on Climate Change (IPCC) estimates a warming of 0.85°C from 1880 to 2012.

Some also argue that current extreme weather events are a result of climate change. In August 2015, for the first time ever, three ‘category four’ hurricanes were recorded over the Pacific Ocean simultaneously. Large heatwaves have occurred this year in India and Pakistan. California is experiencing long-lasting drought. Desertification is a growing issue. Speaking in London in September 2015, former US Vice President Al Gore said: ‘Every day the news is like a nature hike through the Book of Revelation.’

Computer climate models are used to predict future climate change (though some criticise them, perhaps overly scrupulously). Meta analyses average out a series of model predictions for researchers to get an average picture of how the climate may change in the future.

Climate models can also be used to hindcast past climate changes. As the IPCC has noted in the past, and in its most recent assessment report (AR5), models can’t replicate the observed temperature changes seen since 1951 when the models are spun up with natural forces and internal variability alone. Only when models take account of anthropogenic forcing do they match the observed record (though there has been a divergence over the last few years due to the models having trouble with predicting chaotic events).

The consensus is that the climate is changing, that humans are now the dominant factor in this change, and that we are locked into a certain amount of warming due to the greenhouse gases we have already emitted. But the complexity of the earth’s chaotic systems means that how it will respond to this forcing is uncertain.

= Climate sensitivity =

A number of comprehensive ocean-atmospheric global circulation climate models are used by various organisations to model future global climate trajectories. These can look at outputs such as temperature, precipitation or sea ice extent in certain areas as well as producing global average temperature paths.

Different models have different parameters and so a range of outcomes can occur depending on the underlying scenario on emissions and the timing of when emissions cuts take place, for example.

Key to the impacts of climate change is how the earth responds to greenhouse gases – or the level of the earth’s‘climate sensitivity’. This can be expressed as the level of eventual global average temperature increase experienced by a given increase in carbon dioxide into the atmosphere. A doubling of carbon dioxide from pre-industrial levels (280 ppm) is used to compare model responses.

The climate sensitivity is uncertain. It is almost certainly not below 1°C for a doubling of carbon dioxide, and it is unlikely to be above 6°C. The IPCC has slightly changed its wording on climate sensitivity in its recent reports, and in AR5 it says with medium confidence that it is likely to be between 1.5°C and 4.5°C. Quite a difference in temperature, and thus the associated impacts.

[[File:Climatechange2.png|link=File:Climatechange2.png]]

Change in global mean surface temperature relative to 1986–2100 for two IPCC scenarios – red largely represents business as usual while the blue scenario represents action on emissions. The shaded areas represent the uncertainty around the projections from the host of climate models that generated the curves. (Source: IPCC)

= Feedbacks and the 2°C target =

The phenomenon of feedbacks in the climate system is hugely important when it comes to climate and environmental change.

In general terms, negative feedbacks act to dampen the effect of an initial stimulus and can reverse a certain trend. The problem with many climate-related feedbacks is that they are largely positive in nature – they will act to enhance and amplify the effect that was already underway, thus feeding back and intensifying the initial direction of change. Uncertainty around how much of a role feedbacks will play in climate change is part of the reason for the range of climate sensitivity estimates.

A few good examples of climate feedbacks can be found in the upper northern hemisphere, in the Arctic.

=== Melting ice ===

The albedo effect is one. It relates to the amount of shortwave radiation that is reflected by a given surface on the earth. Lighter surfaces such as snow and ice reflect radiation back to the atmosphere and act to perpetuate a cooler local environment. Darker surfaces absorb heat and warm the surrounding area.

As Arctic sea ice and ice on land, for example on the fringes of Greenland, melts due to increasing temperatures in the Arctic, this exposes the darker underlying sea or land. This results in further local warming, reinforcing the original stimulus.

The rate of rapid decline of Arctic sea ice extent over the last 30 years has taken many by surprise, and is partly a result of this feedback. Estimates of when the Arctic will be free of sea ice have been brought forward significantly (which in itself will then feed back into the climate system).

=== Freshwater ===

Further feedbacks abound. The injection of more freshwater into the Arctic Sea as a result of this melting could disrupt the ocean’s thermohaline circulation, which distributes heat around the globe, thus having climatic effects further afield.

Melting permafrost could release vast stores of trapped methane into the atmosphere – clearly not a good thing. The Greenland ice sheet could reach a melting point where internal cryospheric mechanisms are initiated to result in its total, unstoppable collapse, resulting in a 7 m increase in global sea level.

These are the sorts of things touched on when people talk about irreversible, dangerous and runaway climate change. And as discussed earlier, theory says that once certain ‘tipping points’ are passed, the earth’s climate system could flip into an alternate permanent state that could be detrimental to current life on earth.

So, the climate sensitivity is fundamental to whether we may be able to adapt to the consequences of the greenhouse gases we have emitted and are locked into emitting, of whether we may be exposed to environmental turmoil.

This has led to the well-known goal to limit warming to a 2°C rise over pre-industrial temperatures to avoid ‘dangerous’ climate change. This was decided in the 1990s to be an adequate target, but many have argued subsequently that it will still come with significant impacts.

Many in the climate community now regard keeping to below 2°C as unrealistic due to the carbon emissions we are ‘locked into’ under business as usual. The IPCC says it is likely that 450 ppm of carbon dioxide will equate to 2°C, but others argue that we shouldn’t go past 400 ppm (which was reached earlier this year), or even 350 ppm.

= How much more carbon can we emit? =

In AR5, the IPCC for the first time outlined a ‘carbon budget’ – the amount of carbon we can still emit and keep a reasonable chance (66%) of staying below 2°C. Accounting for other warming factors, it set this as a total of 800bn tonnes of carbon on top of pre-industrial levels. We have already emitted around 530bn tonnes, meaning about two thirds of the budget has gone. At current emission rates we will blow the budget in 25 years.

AR5 also stresses the importance of cumulative emissions – i.e. it is better from a total emissions point of view to follow a trajectory of emissions reductions where steeper cuts are made in earlier years than left till the last minute, as the net reduction would be much greater.

Overshooting carbon dioxide targets and then having to take carbon back out of the atmosphere is an option, but geoengineering techniques are viewed with suspicion and many deride them as a bad idea. The IPCC does however explore the ‘Plan B’ option of burning biomass in power stations and then capturing and storing the carbon to produce negative emissions.

Staying below 2°C is seen as a significant challenge. The IPCC says that to do so we need to rapidly deploy a significant additional amount of low carbon power generation and prove carbon capture and storage (CCS) quickly. Bioenergy and CCS (BECCS) may then have a part to play. Most IPCC 2°C scenarios feature some form of BECCS element.

Anthropogenic climate change is indeed a detailed and difficult problem, but what underlies it all? Is it an expression of a deep part of human behaviour in which individual short-termism will always triumph over collective action? That certainly is part of the reason we are in this situation.

But collectively we are taking action by pushing forward low carbon energy solutions and measures on deforestation. We have an innate desire to protect fragile ecosystems and endangered species.

The case for action is clear. The challenge is significant, but a positive outcome is possible. Our way of life depends on it.

This article was written by--[[User:Marc Height|Marc Height]] 11:12, 04 Dec 2015 (BST)

First published in the November 2015 issue of [https://www.energyinst.org/information-centre/ei-publications/energy-world/energy-world-november-2015 Energy World].

= Find out more =

=== Related articles on Designing Buildings Wiki ===

* Albedo.
* Biomass.
* Carbon plan.
* Climate Change Act.
* Emission rates.
* Energy targets.
* Environmental policy.
* Globe temperature.
* Green Deal.
* Greenhouse gases.
* Intergovernmental Panel on Climate Change IPCC.
* Kyoto Protocol.
* Radiation.
* Sustainability.

=== External references ===

* LinkedIn – [https://www.linkedin.com/pulse/cop21-securing-global-deal-climate-need-action-marc-height Climate Change Science]

[[Category:International]] [[Category:Research_/_Innovation]] [[Category:Theory]] [[Category:Sustainability]]

User:Marc Height

2015-12-04T11:12:28Z

Marc Height:

Marc Height is Deputy Editor forEnergy World which covers the entire energy scene – from technology to policy, from people to projects, from renewables to nuclear – and everything in between.