Sensitivity of the Earth System

Rachel James

  • A 1.5°C warmer world is not a safe one. The earth’s temperature has already exceeded 1°C above the preindustrial, and other important changes in the cryosphere, oceans, and biosphere have been detected, notably glacier loss and coral bleaching. We cannot assume that an even warmer world will be safe: 1.5°C implies even larger changes in earth systems.

 

  • Science suggests that limiting to 1.5°C would avoid some dangerous climate change impacts, but our understanding of the difference between 1.5°C and 2°C is in its infancy. Our existing understanding of the sensitivity of earth systems suggests that limiting to 1.5°C would avoid some dangerous changes which would be expected at 2°C. However, understanding the exact impacts of 1.5°C, and the difference between 1.5°C and 2°C is challenging, due to limited previous research focusing on these mitigation targets, a lack of climate model experiments designed to model 1.5°C, and large uncertainties.

 

  • A 1.5°C world is not just “less warm” than 2°C. There are feedbacks in the climate system which mean that there could be nonlinear responses to global warming: impacts of 2°C might be qualitatively different from impacts of 1.5°C, especially for oceans and polar regions. The sensitivity of earth systems to a 1.5°C or 2°C world might also be determined by the impact of mitigation technologies, and whether there is temperature overshoot.

Regional Impacts

Boipelo Tshwene-Mauchaza

  • The talks, plenary sessions, poster sessions on regional climate impacts of 1.5 focused on exploring the probable consequences of climate changes at 1.5◦C pathway, at a continental and sub continental scale regions. Assessment of global warming impacts at this scale is of interest to decision makers.

 

  • However coherent information about regional climate change impacts is limited. Further research gaps surfaced on the rate of change and regional dimensions on the impacts of 1.5◦C and the difference between 1.5 and 2°C.

 

  • From a regional impact perspective, the pinnacle of discussions was understanding the urgency and importance of keeping global temperature rise ‘well below’ 2 °C and limiting it to 1.5 °C. The community explored from a scientific, quantitative perspective the disparity between a 1.5◦C increase and a 2◦ C increase.

 

  • Here are some key regional examples of discernible disparity brought about by an extra 0.5 discussed:

    • For the African continent, a 0.5 °C rise has the potential to cause devastating biodiversity impacts. The higher the rise in temperature, the greater the risk of reaching a tipping point to the extent where biodiversity cannot recover (Professor Mahli).

    • Drying change: 0.5°C extra will lead to increases in the duration of dry spells in regions such as Southern Africa, and Mediterranean, these exacerbating drought events (Dr. Carl Friedrich Schleussner).

    • Wetting change: an amplified 0.5°C global temperature shows increase in heavy precipitation events in many regions, with a high likelihood in the Mid-latitude and the tropics.

    • Global crop yields: 0.5°C surplus will lead to the reduction in the feasibility of food crops especially in the African continent where corn yields are to decline by about half (Dr. Stéphane Hallegate). High local mean temperature change significantly reduces the percentage of crop yields, in both the Temperate and Tropical climate regions.

  • It is crucial to keep in mind that an average of 1.5 (or 2)°C means some regions will suffer much higher temperature increase. Professor Sonia Seneviratne for instance finds that on a 1.5°C pathway, temperature extremes in the Arctic could rise by 4.4°C and by 2.2°C around the Mediterranean basin.

 

  • In using and interpreting the estimates, it is imperative to keep in mind that there exist uncertainties in the character, magnitude and rates of future climate change.

Human Impacts of 1.5 ⁰C

Ruksana Rimi

  • It is a challenge to understand how humans are going to respond to the climate change in next 100 years. Along with the deviations in the human exposure to sea level rise (SLR), cyclones, floods, and droughts; there will also be changes in disaster preparedness, adaptation capacity and mitigation pathways. An appropriate quantification of the human impacts is challenging as it needs to consider all likely positive and negative aspects.  

 

  • Human impacts of 1.5°C have been addressed inadequately by the climate researchers. This calls for more comprehensive studies using the multi-indicators’ assessment and risk management framework on regional as well as global scales. However, climatic and non-climatic influences need to be carefully identified while studying human impacts from extreme weather events. How private sectors can play a role in managing human impacts will be useful to know in future.

 

  • Early onset of impacts in the Himalayan mountainous region is anticipated by researchers, as “1.5°C global warming would be actually 2.0°C for the Ganges-Brahmaputra-Mehgna basin in this region, making people more vulnerable to climate change impacts.” This indicates how human impacts can be more severe at some geographical locations. 

 

  • How far can a small island country go to adapt? Maldives built an artificial island, Hulhumalé, in 1990s with a mean elevation of 2m above mean sea-level. Over longer timescales (e.g.  > century), where temperatures may stabilize, but sea-levels keep rising; incremental larger-scale government led adaptation for Hulhumalé is advised. Question is how far a small island country like Maldives can go to adapt when 1.5°C warmer world means accelerated SLR. 

 

  • A hot spot for climate change impacts, Bangladesh is already experiencing climate change impacts and frequent weather events in a short time scale affecting the agricultural production and food security, water resources management and overall economy of the country. How ‘loss and damage’ can be taken into consideration when and where adaptation goes beyond the capacity of the human – is now an issue to be studied for this country and others with the same conditions. 

 

  • Economic impact assessments can be benefitted by looking at factors beyond GDPs and applying multi-indicators assessments. Studies on the 1.5°C human impacts at different countries with low and high climate vulnerabilities should be conducted addressing living standards, health, education, livelihoods, social security, etc.

Implications of a 1.5 ⁰C target for adaptation

Frank Sperling

  • Adaptation is already a necessity: Many livelihoods and economic sectors are already vulnerable to current climate variability and observable shifts in climatic conditions. Adaptation to climate change has to be viewed as part of a comprehensive risk management effort to ensure the sustainability of development progress;

 

  • Avoided impacts: Limiting global warming to 1.5 °C above pre-industrial levels reduces the exposure to some climatic extremes, such as extreme heat or precipitation events. While there are still considerable uncertainties with regards to the avoided impacts by constraining global warming to 1.5 °C instead of 2 °C, lower levels of warming are associated with a lower risk of crossing catastrophic tipping points in the earth system, which are difficult to reverse and may be beyond the adaptive capacity of some societies or countries;

 

  • Mitigation, adaptation and sustainable development: When considering mitigation options for a 1.5 °C warming trajectory, decision-makers also need to be conscious about the interactions of their strategic choices with climate change adaptation and development objectives. This particularly applies particularly in the land-use context, where a one-sided focus on bioenergy carbon capture and storage (CCS) may create conflict with food security concerns and hence exacerbate local level vulnerabilities. An emphasis on and upscaling of mitigation measures, which focus on synergies between land productivity and mitigation concerns, such as soil carbon management and biochar, can help avoid such conflicts, while a focus on demand side management, such as sustainable consumption, can provide additional space for development, which is critical for reducing the vulnerabilities of the poor;

 

  • In conclusion, limiting global warming to 1.5 °C will likely help humanity to avoid climate change impacts that it cannot manage, but mitigation pathways need to be carefully chosen by addressing multiple policy objectives in order to minimize trade-offs and enhance synergies with other development and environmental concerns.

Mitigation Pathways to 1.5°C

Christopher Roney

  • Emissions pathways must peak early, rapidly decarbonize, and reach net zero, and the carbon budget to do so is very likely between 60 and 300 GtC with midrange estimates around 200 GtC.

 

  • Most pathways to 1.5°C overshoot and then return to the target, and the scale and duration of that overshoot may be as important as the final temperature.

  • Recalcitrant emissions such as those from aviation, shipping, and agriculture need to be mitigated  through demand reduction, or extensive carbon removal separate from the point source will be necessary.

 

  • The research and modelling community needs to consider mitigation as a process of systemic  social and technological transformation, rather than one of marginal abatement. 

 

  • The aggressive pace required to reach 1.5°C means that research into the potential, cost, and side effects of technologies (SRM, direct air capture, BECCS, etc.) must be conducted to define the possibility space and trade offs for mitigation pathways.

 

  • Mitigation pathways must be designed with an understanding of the demands of and implications for sustainable development, both ethically and practically. Setting and meeting the 1.5°C target is as much an ethical problem as it is sociotechnical.

Technology Options for Mitigating 1.5°C

Sam Hampton

  •  The scale of the challenge for achieving 1.5C means that 80% of global integrated assessment models use Negative Emissions Technologies (NETs) in their simulations.

 

  •  There are range of different NETs, including bio-energy with carbon capture and storage (BECCS), direct air capture (DAC), and solar radiation management (SRM). However none will be economically viable at scale in the near future, and raise serious ethical and governance questions.

 

  •  There was consensus that strong mitigation actions to reduce emissions in the near term were essential in all scenarios, even those which include NETs in future. However some contributors felt that debate on NETs diverted attention away from the urgency of these actions.

Financing 1.5°C

Lucas Kruitwagen

  • The transition to a 1.5oC warming pathway largely depends on the ability to finance zero-carbon development in the Global South

 

  • Eliminating fossil fuel subsidies and capturing carbon externalities are essential to align incentives for zero-carbon investment

 

  • The political entrenchment of the fossil fuel industry must be overcome to successfully redirect capital

 

  • Countries in the Global South are assessed to carry excessive political risk, which prevents investment and disproportionately affects CAPEX-intensive renewables relative to OPEX-intensive fossil-fired electricity generation

 

  • Climate finance has excessive measuring, reporting, and verifying requirements which increase costs

 

  • Public finance and state development banks play a key role in de-risking private sector investment

 

  • New green finance vehicles like green bonds show promise by standardising and aggregating climate solution investment opportunities

Societal & Development Implications of the Paris Agreement

Emilie Parry

  • The 1.5°C commitment at COP21 was a policy (and politically-led) choice, not a scientifically led or informed determination. Sustainable development and social justice concerns were the drivers for the 1.5°C commitment. Lesser Developed Countries (LDCs), developing nations, and Small Island Developing States see the 1.5ºC agreement as a climate justice ‘win’ for most vulnerable populations worldwide, for whom 0.5ºC temperature rise will make the greatest difference terms of weathering impacts.

 

  • There is a need to integrate discourse on the 1.5°C cap (and strategies to achieve it) across disciplines—not only at the point of convergence when agreements are made, but throughout the processes of discovery and solution seeking, including in sustainable development, humanitarian, and social policy and praxis realms.  The goal of capping at 1.5°C has no chance of being met without bringing ‘everyone to the table’ in collaborative discourse and strategic planning. 

 

  • Research Funding: There is a need for more research funds to be invested into adaptation, adaptation and mitigation combined, metrics for understanding overlaps and distinctions between climate change adaptation, development and humanitarian efforts The 2015 SDGs including climate change may help open the door to funding that overlaps with climate mitigation and adaption, and resilience.

  • There is much to learn from the most climate- vulnerable populations and countries around the world. While historically they have contributed very little to the current eco-crises the planet is experiencing, they have been hit first and the hardest by the unpredictable impacts and aggravating factors linked to climate change. During the past 10-15 years in particular, the poorest of the poor and most vulnerable populations have developed stronger resilience, innovative and low-tech, low-cost sustainable mitigation and adaptation strategies, along with risk reduction and risk management. These people have a lot to teach the rest of the world, and can offer models for solutions, as well as collaborative strategies for mitigation and adaptation, if they are brought into discussions (with equitable engagement and roles to play).

Implications of 1.5°C for Governance

Lydia Messling

  • The decision to stay below 1.5°C warming is one based on values. And similarly, the decisions as to what mitigative measures to make, which adaptation actions to take are also a value-based decision. What the science can tell decision-makers is what the available options are and the potential consequences. However, it will remain a decision based on values that will determine our trajectory of climate change, and the biggest question is if we need to change our values in order to keep warming to below 1.5°C.

 

  • The Paris Agreement represents a recalibration of ambition. In policy circles, the possibility of 4°C of global warming was beginning to become a commonplace assumption. Whilst 1.5°C may not be achievable, the Paris Agreement has reset ambitions significantly.

 

  • There is a need for national and local implementation of this international commitment to happen very soon. Business and education systems need to reflect this too, but it is not clear what path these will take to reach 1.5°C, particularly if we are looking at having overshoot and NETs.

 

  • Where does justice fit in with this? Arguably, the reason why 1.5°C has become a focus is because it was pushed for by those who are going to be affected first by climate change. A sense of justice is driving this international commitment to keep to 1.5°C. The question for governance then is how much is a just outcome worth? This may challenge societies’ values, and these may need to change in order for us to see the transformation needed to keep to 1.5°C.

 

  • Governance also needs to adapt to the mitigation methods that will be required to stay below 1.5°C. There will be some difficult decisions to make – need to manage the transition.

 

  • Scientific uncertainty does not permit political stalling and a special report on 1.5°C will not create scientific certainty. Science, however certain or uncertain, can only ever inform a values-based decision, but it is up to decision-makers to decide under what values those decisions are made.

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CONCLUSIONS

Summary of key messages and rapporteur reports from the 1.5 Degrees conference (20-22 September 2016):

 
 
 
 
 
 
 
 
 

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Conference organised by: 

Environmental Change Institute

Oxford University

South Parks Road, Oxford, OX1 3QY

United Kingdom