Tag Archives: Paris Agreement

Simple approximations can link emissions and temperature rise

Some simple indicators based on stylised emissions tracks help show clearly the consequences of different rates of emissions reductions.

A simple relationship allows the overall objectives – limiting temperature rises and reducing emissions – to be linked in a straightforward way[i]. Over relevant ranges and timescales temperature rise varies approximately linearly with cumulative emissions of CO2, after adjusting for the effect of other greenhouse gases.  Specifically, for every 3700 GtCO2 emitted (1000GtC) the temperature will rise by about 2.0 degrees[ii] (with estimates in the range 0.8 to 2.5 degrees)[iii].  This is the transient climate response to cumulative emissions (TCRE).

There has been around a 1.0 degree rise in temperatures to date[iv].  This means the remaining total of cumulative emissions (“carbon budget”) needs to be small enough to keep further temperature rises to around 0.5 to 1.0 degrees if it is to meet targets of limiting temperature rises to 1.5 to 2.0 degrees.

The remaining carbon budget for meeting a 1.5 degree target (with 50% probability) is around 770 GtCO2.  The remaining carbon budget for meeting a 2 degree target (again with 50% probability) is 1690 GtCO2[v].  This is illustrated in Chart 1, which shows temperature rise (median estimates) against additional emissions from 2018.

There are many uncertainties in the estimates of the remaining carbon budget.  These include different estimates of the climate sensitivity, variations in warming due non-CO2 pollutants, and the effect of additional earth system feedbacks, including melting of permafrost.  These can each change the remaining carbon budget by around 200GtCO2 or more.

Chart 1: Temperature rise from additional emissions

 

Source: adapted from Table 2.2 in http://report.ipcc.ch/sr15/pdf/sr15_chapter2.pdf

To look at the implications of this simple relationship we can make the following assumptions about future levels of emissions.  These are simplistic, but like all useful simplifications, allow the essence of the issue to be seen more clearly.

  1. Net emissions continue approximately flat at present levels (of around 42 GtCO2a.[vi]) until they start to decrease.
  2. Once net emissions start decreasing they continue decreasing linearly to reach zero – when any continuing emissions are balanced by removals of COfrom the atmosphere. They then continue at zero. There are of course many other emissions tracks leading to the same cumulative emissions.  For example, many scenarios include negative total emissions, that is net removal of carbon dioxide from the atmosphere, in the second half of the century.
  3. Relatively short-lived climate forcings, such as methane, are also greatly reduced, so that they eventually add about 0.15 degrees to warming[vii].

Chart 2 shows various temperature outcomes matched to stylised emissions tracks.  Cumulative emissions are the areas under the curvesTo limit temperatures rises to 1.5 degrees, emissions need to fall to zero by around 2050 starting in 2020, consistent with the estimates in the recent IPCC report[viii].

For limiting temperature rises to 2 degrees with 50% probability, zero emissions must be reached around 2095To reach the 2 degree target with 66% probability emissions need to be reduced to net zero about 20 years earlier – by around 2075 from a 2020 start.  |To reach a target of “well below” 2 degrees is specified in the Paris Agreement emissions must be reduced to zero sooner.

Chart 2: Stylised emissions reduction pathways for defined temperature outcomes (temperatures with 50% and 75% probability)

This simplified approach yields some useful rules of thumb.

Each decade the starting point for emissions reductions is delayed (for example from 2020 to 2030) adds 0.23 degrees to the temperature rise if the subsequent time taken to reach zero emissions is the same (same rate of decrease – i.e. same slope of the line) – see Chart 3 below. This increase is even greater if emissions increase over the decade of delay.  This is a huge effect for a relatively small difference in timing.

Delaying the time taken to get to zero emissions by a decade from the same starting date (for example reaching zero in 2070 instead of 2060) increases eventual warming by 0.11 degrees.

Correspondingly, delaying the start of emissions reductions increases the required rate of emissions reduction to meet a given temperature target.  For each decade of delay in starting emissions reductions the time available to reduce emissions to zero decreases by two decades.  For example, tarting in 2020 gives about 75 years to reduce emissions to zero for a 2 degrees target.  Starting in 2030 gives only 55 years to reduce emissions from current levels to zero once reductions have begun, a much harder task.

Chart 3: Effect of delaying emissions reductions (temperatures with 50% probability)

These results are, within the limits of the simplifications I’ve adopted, consistent with other analysis (see notes at the end for further details)[ix].

How realistic are these goals? Energy infrastructure often has a lifetime of decades, so the system is slow to change.  Consistent with this, among major European economies the best that is being achieved on a sustained basis is emissions reductions of 10-20% per decade.  While some emissions reductions may now be easier than they were, for example because the costs of renewables have fallen, deeper emissions cuts are likely to be more challenging.  This implies many decades will be required to get down to zero emissions.

All of this emphasises the need to start soon, and keep going. The recent IPCC report emphasised the challenges of meeting a 1.5 degree target.  But even the target of keeping temperature rises below 2 degrees remains immensely difficult.  There is no time to lose.

Adam Whitmore – 23rd October 2018

Notes

[i] This analysis draws on previous work by Stocker and Allen, which I covered a while back here: https://onclimatechangepolicydotorg.wordpress.com/2013/12/06/early-reductions-in-carbon-dioxide-emissions-remain-imperative/

[ii] This is the figure implied in Table 2.2 in http://report.ipcc.ch/sr15/pdf/sr15_chapter2.pdf.  All references to temperature in this post are to global mean surface temperatures (GMST).

[iii] IPCC Fifth Assessment Report, Synthesis Report, Section 2.2.4 for the range.  The central value is that which appears to have been used to construct Table 2.2 of http://report.ipcc.ch/sr15/pdf/sr15_chapter2.pdf

[iv] The IPCC quotes 0.9 degrees by 2006-2015, which is consistent with 1.0 degrees now.

[v] Table 2.2 of http://report.ipcc.ch/sr15/pdf/sr15_chapter2.pdf

[vi]  http://report.ipcc.ch/sr15/pdf/sr15_spm_final.pdfC1.3

[vii] See IPCC 1.5 degree report Chapter 2 for details.

[viii] http://report.ipcc.ch/sr15/pdf/sr15_spm_final.pdf summary for policy makers, see charts on p.6

[ix] See for example work by Climate Action Tracker https://climateactiontracker.org/global/temperatures/, and and the Stocker and Allan analysis cited as reference (i) above.  The recent IPCC report Chapter 2 Section C1, concludes:  In model pathways with no or limited overshoot of 1.5°C, global net anthropogenic CO2 emissions decline by about 45% from 2010 levels by 2030 (40–60% interquartile range), reaching net zero around 2050 (2045–2055 interquartile range). For limiting global warming to below 2°C CO2 emissions are projected to decline by about 20% by 2030 in most pathways (10–30% interquartile range) and reach net zero around 2075 (2065–2080 interquartile range). Non-CO2 emissions in pathways that limit global warming to 1.5°C show deep reductions that are similar to those in pathways limiting warming to 2°C.”  References in this paragraph to pathways limiting global warming to 2C are based on a 66% probability of staying below 2C.

 

 

Satellite data can help strengthen policy

Advancing satellite technology can improve monitoring of emissions.  This will in turn help make policies more robust.

There are now around 2000 satellites in earth orbit carrying out a wide range of tasks.  This is about twice as many as only a decade ago[i].   Costs continue to come down, technologies are advancing and more organisations are making use of data, applying new techniques as they do so.   As progress continues, satellite technologies are positioned to make a much larger contribution to monitoring greenhouse gas emissions.

Tracking what’s happening on the ground

Satellites are critical to tracking land use changes that contribute to climate change, notably deforestation.   While satellites have played an important role here for years, the increasing availability of data is enabling organisations to increase the effectiveness of their work.  For example, in recent years Global Forest Watch[ii] has greatly increased the range, timeliness and accessibility of its data on deforestation.  This in turn has enabled more rapid responses.

This is now extending to other monitoring.  For example, progress on construction projects can be tracked over time.  This enabled, for example, monitoring the construction of coal plant in China, which showed that construction of new plants was continuing[iii].

Monitoring operation and emissions

As the frequency with which satellite pictures are taken increases, it becomes possible to monitor not only construction and land use changes, but also operation of individual facilities.  For example, it is now becoming possible to track operation of coal plant, because the steam from cooling towers is visible[iv].  This can in turn allow emissions to be estimated.

More direct monitoring of emissions continues to develop.  Publicly available data at high geographic resolution on NOx, SOx, particulates and in the near future methane[v] are becoming increasingly available[vi].   For example, measuring shipping emissions has traditionally been extremely difficult, but is now becoming tractable, at least for NOx.

Measuring methane is especially important.  Methane is a powerful greenhouse gas with significant emissions from leakage in natural gas systems.  Many of these emissions can easily be avoided at relatively low cost, leading to highly cost-effective emissions reduction.

Monitoring CO2

CO2 is more difficult to measure than other pollutants, in part because it disperses and mixes in the atmosphere so rapidly.  However, some of the latest satellites have sophisticated technology able to measure CO2 concentrations very accurately[vii].  These cover only quite small areas at the moment but are expected to scale up and allow more widespread direct monitoring.  The picture below shows a narrow strip of the emissions from a coal plant in Kansas, based on data from the Orbiting Carbon Observatory 2 (OCO‐2) satellite.  These estimates conform well with reported emissions from the plant.

Figure 1:  Satellite data showing CO2 emissions for a power plant in Kansas

Note: the red arrow shows prevailing wind direction.

Space agencies around the world are now exploring how such monitoring can be taken further.  For example, the EU has now asked the European Space Agency to design a satellite dedicated to monitoring CO2.  It is expected to be operational in the 2020s.[viii]

Work is also underway to improve data analysis, so that quantities of emissions can be attributed to individual plants.  Machine learning holds a good deal of promise here as a way of finding and labelling patterns in the very large amounts of data available.  It is likely soon to be possible to monitor emissions from an individual source as small as a medium size coal plant, taking account of wind speed and direction and so forth.

Implications

These developments will make actions much more transparent and subject to inspection internationally.  Governments, scientists, energy companies, investors, academics and NGOs can monitor what is going on.  Increasingly polluters will not be able to hide their actions – they will be open for all to see.  This is turn will make it easier to bring pressure on polluters to clean up their act, potentially including, for example, holding countries to account for their Nationally Determined Contributions (NDCs) under the Paris Climate Agreement.

Improved transparency and robust data are not in themselves solutions for reducing climate change.  Instead, they play an important role in an effective policy architecture.  And the do so with ever increasing availability and quality.  This gives cause for optimism that policies and their implementation can be made increasingly robust.

Adam Whitmore – 12th September 2018

Thanks to Dave Jones for sharing his knowledge on the topic .

[i] https://www.ucsusa.org/nuclear-weapons/space-weapons/satellite-database#.W5Y-7ZNKhcA, https://allthingsnuclear.org/lgrego/new-update-of-ucs-satellite-database,

[ii] https://www.globalforestwatch.org/about

[iii] See here http://www.climatechangenews.com/2018/08/07/china-restarts-coal-plant-construction-two-year-freeze/ for examples

[iv] https://twitter.com/matthewcgray/status/1032251925515968512

[v] http://www.tropomi.eu/data-products/methane

[vi] https://www.scientificamerican.com/article/meet-the-satellites-that-can-pinpoint-methane-and-carbon-dioxide-leaks/

[vii] https://agupubs.onlinelibrary.wiley.com/doi/10.1002/2017GL074702

[viii] https://www.bbc.co.uk/news/science-environment-43926232

 

Emissions reductions from carbon pricing can be big, quick and cheap

The UK carbon tax on fuel for power generation provides the most clear-cut example anywhere in the world of large scale emissions reductions from carbon pricing.   These reductions have been achieved by a price that, while higher than in the EU ETS, remains moderate or low against a range of other markers, including other carbon taxes.

The carbon price for fuels used in power generation in the UK consists of two components.  The first is the price of allowances (EUAs) under the EUETS.  The second is the UK’s own carbon tax for the power sector, known as Carbon Price Support (CPS).  The Chart below shows how the level CPS (green bars on the chart) increased over the period 2013 to 2017[i].  These increases led to a total price – CPS plus the price of EUAs under the EUETS (grey bars on the chart) – increasing, despite the price of EUAs remaining weak.

This increase in the carbon price has been accompanied by about a 90% reduction in emissions from coal generation, which fell by over 100 million tonnes over the period (black line on chart).   Various factors contributed to this reduction in the use of coal in power generation, including the planned closure of some plant and the effect of regulation of other pollutants.  Nevertheless the increase in the carbon price since 2014 has played a crucial role in stimulating this reduction in emissions by making coal generation more expensive than gas[ii].  According to a report by analysts Aurora, the increase in carbon price support accounted for three quarters of the total reduction in generation from coal achieved by 2016[iii].

The net fall in emissions over the period (shown as the dashed blue line on chart) was smaller, at around 70 million tonnes p.a. [iv] This is because generation from coal was largely displaced by generation from gas. The attribution of three quarters of this 70 million tonnes to carbon price support implies a little over 50 million tonnes p.a. of net emission reductions due to carbon price support.   This is equivalent to a reduction of more than 10% of total UK greenhouse gas emissions.  The financial value of the reduced environmental damage from avoiding these emissions was approximately £1.6 billion in 2016 and £1.8 billion in 2017[v].

Chart:  Carbon Prices and Emissions in the UK power sector

The UK tax has thus proved highly effective in reducing emissions, producing a substantial environmental benefit[vi].  As such it has provided a useful illustration both of the value of a floor price and more broadly of the effectiveness of carbon pricing.

This has been achieved by a price that, while set at a more adequate level than in the EU ETS, remains moderate or low against a range of other markers, including other carbon taxes.  CPS plus the EUA price was around €26/tCO2 in 2017 (US$30/tCO2).  The French the carbon tax rose from €22/tCO2 to €31/tCO2 over 2016-2017. In Canada for provinces electing to adopt a fixed price the carbon price needs to reach CAN$50/tCO2 (€34/tCO2) by 2022[vii].  These levels remain below US EPA 2015 estimates of the Social Cost of Carbon of around €40/tCO2 [viii].

This type of low cost emissions reduction is exactly the sort of behaviour that a carbon price should be stimulating, but which is failing to happen as a result of the EU ETS because the EUA price is too low.  More such successes are needed if temperature rises are to be limited to those set out in the Paris Agreement.  This means more carbon pricing should follow the UK’s example of establishing an adequate floor price.  This should include an EU wide auction reserve for the EUETS.  The reserve price should be set at somewhere between €30 and €40/t, increasing over time.  This would likely lead to substantial further emissions reductions across the EU.

Adam Whitmore – 17th January 2018

Notes:

[i] Emissions date for 2017 remains preliminary.  UK carbon price support reached at £18/tCO2 (€20/tCO2) in the fiscal year 2015/6 and was retained at this level in 2016/7.  In 2013/4 and 2014/5 levels were £4.94 and £9.55 respectively.  This reflected defined escalation rates and lags in incorporating changes in EUA prices. https://www.gov.uk/government/uploads/system/uploads/attachment_data/file/293849/TIIN_6002_7047_carbon_price_floor_and_other_technical_amendments.pdf and www.parliament.uk/briefing-papers/sn05927.pdf

[ii] http://www.theenergycollective.com/onclimatechangepolicy/2392892/when-carbon-pricing-works-2

[iii] https://www.edie.net/news/6/Higher-carbon-price-needed-to-phase-out-UK-coal-generation-by-2025/

[iv] Based on UK coal generation estimated weighted average emissions intensity of 880gCO2/kWh, and 350gCO2/kWh for gas generation.

[v] 50 million tonnes p.a. at a social cost of carbon based on US EPA estimates of $47/tonne (€40/tonne).

[vi] There is a standard objection to a floor in one country under the EUETS is that it does not change of the overall cap at an EU level so, it is said, does not decrease emissions.  However this does not hold under the present conditions of the EUETS, and is unlikely to do so in any case.  A review of how emissions reductions from national measures, such as the UK carbon price floor, do in fact reduce total cumulative emissions over time is provided was provided in my recent post here.

[vii] The tax has now set at a fixed level of £18/tonne.  It was previously set around two years in advance, targeting a total price comprising the tax plus the EUA price.  There was no guarantee that it would set a true floor price, as EUA prices could and did change a good deal in the interim.  Indeed, in 2013 support was set at £4.94/tCO2, reflecting previous expectations of higher EUA prices, leading to prices well below the original target for the year of £16/tCO2 in 2009 prices (around £17.70 in 2013 prices). See https://openknowledge.worldbank.org/handle/10986/28510?locale-attribute=en.  The price is also below the levels expected to be needed to meet international goals (see section 1.2), and below the social cost of carbon as estimated by the US EPA (see https://onclimatechangepolicydotorg.wordpress.com/carbon-pricing/8-the-social-cost-of-carbon/ and references therein).

[viii] Based on 2015 estimates.

New long term targets for emissions reduction are needed.

The UK and other jurisdictions need to set target dates for reaching net zero greenhouse gas emissions.  These need to be reinforced by new targets for 2060 that are at least close to zero, and by reaffirmed or strengthened targets for 2050.

Ten years ago setting emissions reduction targets for 2050 was a major step forward

2018 sees the tenth anniversary of the UK’s Climate Change Act[i].  This remarkable piece of legislation established a legally binding obligation for the UK to reduce its greenhouse gas emissions by 80% from 1990 levels by 2050, with obligations along the way in the form of five year carbon budgets.  So far progress has been remarkably good, though significant challenges remain.

Other jurisdictions also adopted 2050 targets at around the same time.  In 2005 California also set a target of an 80% reduction from 1990 levels[ii].  In October 2009 the EU established a long term EU goal for reducing emissions by 80-95% from 1990 levels by 2050[iii].

At the time these targets were path breaking.  However, ten years on there are good reasons for reviewing and extending them.

But now the world has moved on …

  • When the targets were established, the period to 2050 seemed long enough to give appropriate strategic guidance to policy makers and investors. However, future dates are now ten years closer.  A 2060 target now gives about the same time horizon for planning as the 2050 targets did when they were established.
  • The Paris Agreement sets targets to limit temperature rises which imply stringent limits on cumulative emissions. It also sets a goal of net zero global emissions in the second half of the century.
  • A fifth or more of the world’s carbon budget that remained in 2008 has since been used up[iv], increasing the urgency of emissions reductions.

Extending targets to reflect these changes would have some clear benefits … 

Together these changes imply a strong case for setting new targets now.

The most compelling target would be a date by which emissions must fall to net zero.  Such a target would make it clear to all sectors that they need to completely decarbonise by a specified date.  At the moment emissions of up to 20% of 1990 levels are allowed even in 2050.  This allows each of those sectors where decarbonisation is more difficult – for example parts of industry, agriculture or residential heating – to largely continue in a belief that there will still be plenty of room for them within the 2050 emissions limit, even though this cannot be true for most sectors.  This in turn allows them to continue to believe they can carry on indefinitely without taking the steps needed to decarbonise.  A date for reaching zero makes it clear this can’t happen.

Setting stringent target for 2060 – at or close to zero – would also give investors in low carbon infrastructure greater confidence, and deter investment in higher carbon alternatives. In the case of the UK and California, a simple extrapolation of their current targets would suggest a 2060 target of a 93% reduction from 1990 by 2050, reaching zero by 2065.

As part of the process of setting these longer term goals the existing 2050 targets need to be at least reaffirmed and preferably tightened.  If this is not done there is the risk that policy makers will simply see the problem as having become more distant, and delay action.  This is the last thing that the climate needs.

2050 targets may also need to be revised …

As a first step, the EU’s target of 80-95% cuts clearly needs to be made more precise.  The current uncertainty of a factor of four in the level of emissions allowed in 2050 is too wide for sensible policy planning.

However the events of the last ten years also raise the question of whether the stringency of the 2050 targets need to be increased, with implications for later periods.  The UK Government’s former Chief Scientific Adviser Sir David King and others have suggested that there is a strong case for the UK seeking to reach net zero emissions by 2050[v].  The difference in cumulative emissions in declining linearly to net zero by 2050 instead of by 2065 is substantial, at a little over 3 billion tonnes – equivalent to about 8 years of current UK emissions.

The goal of reaching zero emissions by 2050 is clearly desirable in many ways.  However there is a risk that it may have unwanted side effects.  The government’s advisory body, the Committee on Climate Change has pointed out that policies are not in yet place even to meet current goals for the fifth carbon budget in around 2030[1].  The route to net zero emissions in 2050 – just over 30 years from now – looks even less clear.  Indeed reaching that goal even by 2065 remains challenging.  If even tighter targets are introduced they may come to be regarded as unrealistic, which may in turn risk weakening commitment to them.  A somewhat slower emissions reduction track may prove a relatively acceptable price to pay for retaining the credibility and integrity of the targets.

Whatever the judgement on this, the need for longer term targets is clear.  Governments need to set dates for reaching net zero emissions.  These need to be supported by targets for 2060 that specify continued rapid reductions in emissions after 2050, and by reaffirmation of 2050 targets, tightening them as necessary.  These new targets will in turn help stimulate the additional actions to rapidly reduce emissions that are ever more urgently needed.

Adam Whitmore – 6th November 2017

 Notes:

[1] https://www.theccc.org.uk/publication/2017-report-to-parliament-meeting-carbon-budgets-closing-the-policy-gap/

[i] https://www.theccc.org.uk/tackling-climate-change/the-legal-landscape/the-climate-change-act/

[ii] https://www.arb.ca.gov/cc/cc.htm

[iii] https://www.consilium.europa.eu/uedocs/complementary measures_data/docs/pressdata/en/ec/110889.pdf

[iv] The calculation is based on data in the IPCC Fifth Assessment Report, Synthesis Report.  This quotes a  cumulative budget of 3700 billion tonnes of CO2 for a two thirds probability of staying below 2 degrees.  Of this 1800 billion tonnes had been used by 2011.  Assuming CO2 emissions of roughly 40 billion tonnes p.a. including land use gives a remaining budget in 2008 of 1920 billion tonnes.  Over the subsequent ten years about 400 million tonnes CO2, which is just over a fifth of 1920 billion tonnes, have been emitted.

[v] http://www.independent.co.uk/environment/ministers-greenhouse-gas-emissions-fail-cut-environment-greg-clark-chief-scientist-david-king-a7969496.html