MENU

Social Channels

SEARCH ARCHIVE


Additional Options
Topic

Date Range

Receive a Daily or Weekly summary of the most important articles direct to your inbox, just enter your email below:

Civil Society helps COP21 Choose the right road to 1.5C degrees
GLOBAL TEMPERATURE
15 December 2015 11:42

Piers Forster: 1.5C is a brave new world

Piers Forster

Piers Forster

12.15.15
Piers Forster

Piers Forster

15.12.2015 | 11:42am
Global temperaturePiers Forster: 1.5C is a brave new world

A guest post from Prof Piers Forster, a professor of physical climate change at the University of Leeds and recipient of the Royal Society Wolfson Merit Award. Forster is also a Carbon Brief contributing editor.

The world has spoken. It wants to limit future temperatures rises to 1.5C above historic levels. To achieve this everything must change.  

The twelfth of December 2015 may well be remembered as the day the human race came together and saved the world. Old differences between rich and poor, west and east were laid aside. Unbeknownst to anyone, six months ago and in secret, the sinking Marshall islanders started to raise an army of more than 100 ambitious nations that rose above the flotsam and jetsam of self-interest and created a stronger climate agreement than anyone thought possible.

The Paris agreement aims to hold the increase in the global average temperatures to “well below 2C above pre-industrial levels” and to “pursue efforts to limit the temperature increase to 1.5C”. It also requires parties to produce audited emission-reduction commitments ratcheting up every five years, and delivers a “floor” of $100 billion per year of financing up to 2025.

So unexpected was this that we climate scientists were caught napping. Before Paris, we all thought 2C was a near-impossible target and spent our energies researching future worlds where temperatures soared. In fact, there is still much to discover about the specific advantages of limiting warming to 1.5C, and the plausible social and economic pathways that might keep us under this limit.

However, the research there is points towards some important benefits of a 1.5C warming limit when compared to 2C. As described in a study published last week by Nature Geoscience, the pace of climate impacts can increase drastically at or before 2C of warming. For example, as you can see in the graphs below, the proportion of coral reefs and land for staple crops affected by warming increases rapidly between 1.5C and 2C.

Graphs showing climate change impacts on various sectors per degree of warming.

Climate change impacts on various sectors per degree of warming. Shown as impact by proportion of each sector affected (left) and as a proportion of the total maximum potential impact that climate change could have (right). In other words: the left-hand chart shows how much of a sector is affected by climate change, and the right-hand chart shows how severe that impact is. Source: Ricke et al. (2015).

Some have derided the 1.5C target as a pipe dream, given that current national pledges to reduce carbon dioxide emissions – known as Intended Nationally Determined Contributions (INDCs) – could bring us closer to 3C. However, the limited research that does exist suggests that it is possible to overshoot 1.5C and return below it by 2100. And the figure below illustrates how a five-year ratchet mechanism of increasingly ambitious INDCs could deliver a temperature close to 1.5C by 2100.

Graph that illustrates how a five-year ratchet mechanism could reach the long-term temperature target ambitions by approaching net-zero emissions of greenhouse gases after 2050.

Illustrates how a five-year ratchet mechanism could reach the long-term temperature target ambitions by approaching net-zero emissions of greenhouse gases after 2050. Chart shows CO2 emissions (blue bars), anthropogenic sinks of greenhouse gas emissions (red bars), example INDC trajectories (green lines), and the temperature change (black line). Bars above zero (on left-hand axis) indicate emissions into the atmosphere, while bars below zero indicate gases being removed from the atmosphere (negative emissions). Emissions and temperature change are taken from the IMAGE SSP1-2.6 model in the Shared Socioeconomic Pathway (SSP) version 1.0 database. Figure by Piers Forster.

In many ways, the answer to achieving a 1.5C pathway is simple: we need everything and we need it now. Historic emissions are still warming the oceans so even if emissions were to stop tomorrow we still might pass 1.5C.

Low-carbon transitions require huge changes to infrastructure and societal behaviour that don’t happen overnight. This is where the fun begins, because 1.5C means we will require everything in our arsenal: renewable energy, nuclear power, a dash from coal to gas, zero-carbon transport, energy efficiency, housing changes, low-carbon thermal heating and cooling systems. Even international aviation and shipping that were excluded from this report will need to be tackled within the next few years.

In particular, we will need large amounts of afforestation and carbon capture and storage. Given the lags in the system, even this world-transforming revolution is unlikely to be enough to prevent an overshoot lasting several decades.

Measures that have a more immediate effect on surface temperature will also be required. Mitigation of short-lived climate pollutants, principally methane from agriculture and black carbon (soot) from wood stoves and transport, can help rapidly cool the climate. The short-term cooling from such measures are rather redundant without strong CO2 mitigation at the same time, but with mitigation in place, they are the most effective way of shaving-off overshooting scenarios.

You can see this in the chart below. The red line shows the likely temperature response from the IPCC’s RCP2.6 scenario, where emissions are curbed to keep global average temperature rise to within 2C above pre-industrial levels by 2100. The green line is the same scenario, but with additional reduction in methane. The blue line shows a scenario similar to the current commitments of the INDCs as they stand.

Graph that compares two scenarios that get close to the 2100 target with a scenario illustrative of current commitments.

Compares two scenarios that get close to the 2100 target with a scenario illustrative of current commitments. The Current Commitment is illustrated by the IMAGE-SSP1 Ref scenario. The 2C overshoot is illustrated by the REWIND-MAGPIE-SSP5 2.6 scenario. The 2C limit is illustrated by the IMAGE-SSP1 2.6 scenario. This has additional methane emission reduction compared to the overshooting scenario. Scenarios are taken from the SSP database version 1. Temperatures are computed with the MAGICC6 model. Figure by Piers Forster.

The emission target articulated in Article 4.1 of the Paris Agreement illustrates the level of change needed if the world is serious about halting global warming at such a level, ”to achieve a balance between anthropogenic emissions by sources and removals by sinks of greenhouse gases in the second half of this century”. This wording is clear that atmospheric greenhouse gas concentrations should stop growing soon after 2050, but the meaning of “sinks” is usefully ambiguous.

Sinks can be interpreted as either anthropogenic (large scale carbon capture and storage) and/or natural (relying of forests). It also allows potential trade between greenhouse gases and avoids “zero net carbon emissions” – language that was obviously a line in the sand for some countries as it could imply near-zero fossil fuel use.

After Paris there is lots of work to do to turn the agreement into actions. As scientists, we will also need to work hard to help policy makers choose effective transition pathways and better determine the impacts of unavoidable further global warming.

I for one can’t wait to roll up my sleeves and get started on researching and planning for this brave new world.

Main image: Civil Society helps COP21 Choose the right road to 1.5C degrees. Credit: Takver/Flickr.
Sharelines from this story
  • Guest post from Prof Piers Forster: 1.5C is a brave new world | #COP21 #ParisAgreement
  • Prof Piers Forster on how the world might limit global warming to 1.5C following the adoption of the #ParisAgreement
  • Hello Piers – thanks for that interesting piece. Do we agree that the net-budget arithmetic you project is around this http://www.gci.org.uk/images/Leeds.png

    • Piers Forster

      Nice Figure, Looks about right, note that the idea that the cumulative
      budget represents temperature change really only works cumulative carbon
      emissions – not cumulative GHG emissions

  • Piers Forster

    Nice Figure, Looks about right, note that the idea that the cumulative budget represents temperature change really only works cumulative carbon emissions – not cumulative GHG emissions

    • Hi Piers – I take your point. I also imagine the sink enhancement is carbon only?

      If you’ve got the breakdown (Carbon:non-Carbon emissions and conversions) please share.
      I can separate all that out to get nearer to just the cumulative *carbon* budget.

      • Piers Forster

        table { }td { padding-top: 1px; padding-right: 1px; padding-left: 1px; color: black; font-size: 11pt; font-weight: 400; font-style: normal; text-decoration: none; font-family: Calibri,sans-serif; vertical-align: bottom; border: medium none; white-space: nowrap; }.xl63 { text-align: left; vertical-align: top; background: rgb(162, 189, 144) none repeat scroll 0% 0%; }

        Capture MtCO2/year
        GHG MtCO2eq/yr
        CO2 MtCO2/year

        2005
        0
        43800.33984
        32791.53711

        2010
        0
        47098.94922
        35120.95899

        2015
        0.143119781
        47229.44922
        35484.89177

        2020
        0.286239562
        47359.94922
        35848.82455

        2025
        442.3248179
        42846.41406
        32358.59562

        2030
        884.3633962
        38332.87891
        28868.3667

        2035
        2766.929232
        31955.61914
        23299.25415

        2040
        4649.495068
        25578.35938
        17730.1416

        2045
        6361.203141
        22297.95996
        14745.77706

        2050
        8072.911213
        19017.56055
        11761.41252

        2055
        9591.731851
        16598.25049
        9358.104981

        2060
        11110.55249
        14178.94043
        6954.797445

        2065
        11970.27846
        11104.03125
        4188.835617

        2070
        12830.00443
        8029.12207
        1422.87379

        2075
        13083.36068
        6217.991455
        -214.1795807

        2080
        13336.71692
        4406.86084
        -1851.232951

        2085
        13014.33963
        3888.343872
        -2128.230662

        2090
        12691.96233
        3369.826904
        -2405.228373

  • Paul Matthews

    I wonder if Piers knows what ‘brave new world’ signifies?

    • Piers Forster

      So do I!

      • Wolfgang Cramer

        I am not sure I am getting the punch. I am very pleased about, and in full agreement with the positive tone of your analysis, Piers, but I see nothing particularly Orwellian in this perspective!

        Most importantly, the Paris Agreement shows me how far international politics can go – the rest is up to civil society, and that is all of us.

  • Petra Tschakert

    Nice piece, Piers! But not all climate scientists had been napping :)
    In all modesty, here my contribution to 1.5C after Lima:
    http://climatechangeresponses.biomedcentral.com/articles/10.1186/s40665-015-0010-z

  • Thanks for the numbers Piers. With some ‘smoothing’, I have constructed this image to reflect them as here: – http://www.gci.org.uk/images/Leeds2.png

    The source-emissions budget net of sinks – 417 Gt C – seems high to me, if 1.5°C is the control. Looks to me like temperature slowing later and so higher. But its all rife with unknowns.

    FWIW the model I use is here http://cbat.info/#domain-1

  • Eric Mcoo

    There is no established relationship between human activity and the earth’s climate.


Related Articles

THE BRIEF

Expert analysis directly to your inbox.

Get a Daily or Weekly round-up of all the important articles and papers selected by Carbon Brief by email.

THE BRIEF

Expert analysis directly to your inbox.

Get a Daily or Weekly round-up of all the important articles and papers selected by Carbon Brief by email.