PwC analysis of IPCC Special Report on 1.5°C

09 October 2018

Three years ago in Paris, governments adopted a new, more ambitious, target to limit warming to 1.5°C. They also asked the IPCC to prepare a report on the benefits of 1.5°C compared with the ‘old’ 2°C goal and explore pathways to get there.  The IPCC published this report yesterday - its findings are deeply worrying. Broadly, projected climate change impacts are substantially worse at 2°C compared with 1.5°C.  This applies to impacts on ecosystems, heat stress in cities, droughts, crop yields, flooding and storm damage (among others).

An earlier draft of the report noted “there is no simple answer to the question of whether it is feasible to limit warming to 1.5 degrees and adapt to its consequences”.  All 1.5°C pathways imply rapid emissions reductions to net zero, with a 40-50% reduction on 2010 levels by 2030 and 70-90% reductions by 2050.  In addition to ‘Natural Climate Solutions’ (forest & soil carbon), after 2050 we will need to rely on carbon dioxide removal technologies to achieve deep net negative emissions.  Some refer to these technologies as carbon unicorns as they are currently unproven at scale and allow for a more creative pathway to 1.5°C. The report is clear that changes in behaviour and lifestyles, technology development and deployment, finance, international cooperation and policy are all needed to keep 1.5°C in reach.

There are two frustrating omissions from the report.  First, there is limited detail on the impacts of three or more degrees of warming which is what we are currently on course with. The report aims to justify raising ambition to 1.5 degrees, but there doesn’t appear to be adequate political will even to limit warming to 2 degrees. Our 2018 Low Carbon Economy Index, published last week, shows the gaps between current progress and the 2 degrees goal across the G20. A summary of expected impacts of more significant global warming (that are actually more likely given our current course) would make a much more compelling case for climate action. But this didn’t form part of the terms of reference for the report.

Secondly, the Summary for Policymakers (SPM), the bit of the report that’s most likely to get read, gives limited detail on the value of those impacts. There are only a few references to GDP or economic growth. For example, the SPM describes the impact on crop yields for maize and wheat but doesn’t give details about the implications for prices or availability. These are the things that motivate politicians and business leaders to take action. The only dollar signs relate to the level of energy-related mitigation investment needed to achieve a 1.5C pathway.  Also, the timing of the impacts is generally around 2050 and beyond and yet it is rare that people in companies or politicians seriously think beyond 2030.

The report has a 34-page Summary for Policymakers and 5 chapters covering:

  1. Framing & context
  2. Mitigation pathways compatible with 1.5°C in the context of sustainable development
  3. Impacts of 1.5ºC global warming on natural and human systems
  4. Strengthening and implementing the global response
  5. Sustainable Development, Poverty Eradication and Reducing Inequalities

Here are some of the main points copied from the report:

We have already warmed by 1°C and are expected to breach 1.5°C by around 2040: “Human activities are estimated to have caused approximately 1.0°C of global warming above pre-industrial levels ... Global warming is likely to reach 1.5°C between 2030 and 2052.” (SPM p.4)

The maximum temperature increase depends on the cumulative emissions until we reach net zero.  “The maximum temperature reached is then determined by cumulative net global anthropogenic CO2 emissions up to the time of net zero CO2 emissions (high confidence) and the level of non-CO2 radiative forcing in the decades prior to the time that maximum temperatures are reached (medium confidence)”. (SPM p.5)

2°C is substantially worse than 1.5°C. “Climate models project robust [distinct & statistically significant] differences in regional climate characteristics between present-day and global warming of 1.5°C, and between 1.5°C and 2°C … Risks from droughts and precipitation deficits and heavy precipitation events are projected to be higher at 2°C compared to 1.5°C ... in some regions” (SPM p.8)

“Impacts on biodiversity and ecosystems (such as fisheries and coral), including species loss and extinction, are projected to be lower at 1.5°C of global warming compared to 2°C.” (SPM p.8 & 9). “Coral reefs, for example, are projected to decline by a further 70–90% at 1.5°C (high confidence) with larger losses (>99%) at 2ºC.  Limiting warming to 1.5°C, compared with 2ºC, is projected to result in smaller net reductions in yields of maize, rice, wheat, and potentially other cereals.” (SPM p.11)

“Risks to global aggregate economic growth due to climate change impacts are projected to be lower at 1.5°C than at 2°C by the end of this century. Countries in the tropics and Southern Hemisphere subtropics are projected to experience the largest impacts on economic growth due to climate change should global warming increase from 1.5°C to 2 °C” (SPM p.12)

Poor countries and poor and vulnerable people in all countries are particularly susceptible to the impacts of climate change.  “Populations at disproportionately higher risk of adverse consequences of global warming of 1.5°C and beyond include disadvantaged and vulnerable populations, some indigenous peoples, and local communities dependent on agricultural or coastal livelihoods … Any increase in global warming is projected to affect human health, with primarily negative consequences” (SPM p.11)

“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).” (SPM p.15)

At current level of emissions, there’s about 14 years left for a fair chance of staying within the 1.5oC carbon budget (our LCEI predicted 18 at current rate of decarbonisation): “The associated remaining budget is being depleted by current emissions of 42 ± 3 GtCO2 per year. … Using global mean surface air temperature, as in AR5, gives an estimate of the remaining carbon budget of 580 GtCO2 for a 50% probability of limiting warming to 1.5°C” (SPM p.16)

Natural Climate Solutions will need to play a big role in achieving net negative emissions.  “All pathways that limit global warming to 1.5°C with limited or no overshoot project the use of carbon dioxide removal (CDR) on the order of 100–1000 GtCO2 over the 21st century. Existing and potential CDR measures include afforestation and reforestation, land restoration and soil carbon sequestration, BECCS, direct air carbon capture and storage (DACCS), enhanced weathering and ocean alkalinization.”  (SPM p.23)

If countries follow the trajectories outlined in their Paris Agreement targets, emissions will grow to around 55Gt CO2 by 2030, putting the 1.5°C goal out of reach.  A substantial section of the report focuses on the co-benefits of action to limit warming to 1.5°C in the context of sustainable development. “Limiting the risks from global warming of 1.5°C in the context of sustainable development and poverty eradication implies system transitions that can be enabled by an increase of adaptation and mitigation investments, policy instruments, the acceleration of technological innovation and behaviour changes”. (SPM p.29)

Jonathan Grant | Director, Sustainability & Climate Change, PwC UK
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