A Summary Of The IPCC Report On 1.5 Degrees Of Warming

This report was requested in 2015 at COP21, agreed upon in 2016 and published in 2018. It starts by noting that human activities have already caused a mean temperature rise of 1.0 degrees above preindustrial times with temperatures oscillating between 0.8 degrees to 1.2 degrees. With the current rate of emissions, the first temperature threshold of the Paris agreement which is 1.5 degrees, will be attained between 2030 and 2052. In fact, the emissions trajectory means a rise of 0.2 degrees per decade.

The report further states that warming is taking place throughout the globe, and that higher than normal averages have been reported in multiple places and in various seasons. Warming is greater over land than the sea. It is twice to thrice higher in the Arctic. In fact studies are attributing higher temperatures and weather extremes to climate change. Warming will take place for centuries to millennia to come because of greenhouse gases from preindustrial times to now. However, these alone cannot trigger 1.5 degrees rise, this will be determined by the near future emissions. But they will result to changes in global climate system for a long time.

Attaining and keeping it at net zero carbon emissions and drops in the non-CO2 causes of climate change can pause human caused global warming in a span of decades. The peak temperatures will be decided by the residual amounts of greenhouse gases in the atmosphere at the time of net zero. Net negative technologies (CDR) will have to be deployed to remove more atmospheric emissions in order to halt nature and climate feedbacks (when the system feeds into and accelerates itself), rollback ocean acidification and limit sea level rise.

Effects of climate change are greater at 1.5 than at now, but lower than 2 degrees which is the second threshold. The scale and degree of impacts is determined by geographical location, exposure to impacts, development, level and choices of adaptation, ability to respond, vulnerability, mitigation options and the speed of warming.

Even now human and natural systems have already been affected, with ecosystems and their services already negatively altered. Climate consequences are harsher if global temperatures go beyond 1.5 and come back to this point before the end of the century (2100) than if they slowly peak at and remain stable at 1.5. If the first occurs, some ecosystems might be lost for good.

Notably, mitigation and adaptation is already happening, but the scale and magnitude needs to be more vast, extensive and ratcheted up. This will reduce climate risks. 1.5 degrees will cause more temperature extremes over land and sea, increased amounts of rain, more and stronger droughts. Heavy rains increase flooding and destroy infrastructure. Also the number of hot days will go up in general, with the mid and high latitudes having more extremely hot days and nights. All this would be magnified at 2 degrees.

Sea level rise will continue after 2100 even if temperatures are at a constant of 1.5 degrees. However the magnitude will be determined by future emissions. At 1.5, it can reach 0.77 meters at the higher end giving coasts, communities and islands enough time to adapt however they can. This will save about 10 million people compared to 2 degrees. At 2 degrees the sea level is 0.1 meters higher than 1.5 degrees. Between the two thresholds, instability of Greenland’s ice sheet and marine ice sheet in Antarctica will cause a rise of several meters over centuries to millennia.

The impacts on biodiversity, forest fires, invasive species, and loss of species and extinction is lesser at 1.5 degrees than at 2. Capping warming to 1.5 helps lower impact on terrestrial, freshwater, coastal ecosystems and all their services to mankind. At 1.5 degrees, 6% of insects, 8% plants, 4% vertebrates lose habitat while that figure triples for insects and doubles for the rest at warming of 2 degrees. At the present 1 degree rise, 4% of land ecosystems transform from one type to another while at 2 degrees, 13% change. Keeping it 1.5 reduces impacts by half (50%).

A majestic Kenyan elephant. Its home is threatened(Tsavo Trust)

Ocean acidity and decreases in levels of oxygen exist but are less pronounced at 1.5 than at 2 degrees. This is less harmful to marine biodiversity, ecosystems, aquaculture and fisheries. At 1.5, the Arctic will experience one sea ice free summer per century while 2 degrees result to one of those every ten years. However if the planet overshoots 1.5 degrees but later comes back to this, the effects on Arctic sea ice can be overturned (reversed) in a span of decades. At 1.5, marine species migrate upwards (gradually polewards/high latitudes), while many ecosystems are damaged. Yield from fisheries, aquaculture and all coastal resources diminish. Some estimates on fisheries put this at 1.5 million tonnes lost at 1.5 and 3 million lost at 2 degrees. About 70-90% of coral reefs vanish at 1.5 while at 2 degrees 99% is lost. In fact at 2, a host of ecosystems are irreversibly lost. At 1.5, ocean acidification affects abundance and functions of marine organisms that depend on an alkaline balance in water chemistry. Processes needing that such as breeding, calcification and growth and ultimately the survival of a very numerous and diverse number of organisms is hugely affected.

In the human sphere, impacts on food security, health, water supply, physical security and economic growth are higher at 1.5 degrees than at present, but even higher at 2 degrees. Inequalities will increase as the number of the poor increases. Women and girls, urban poor, environmentally-dependent communities, least developed countries (LDCs), small island developing countries (SIDS), Arctic, Africa and dryland regions all face more climate impacts especially affecting development at 1.5 degrees. However the number of poor is lesser by several hundred million than at 2 degrees.

At 1.5, the number of the human population faced by water stress is half the number at 2 degrees, though this varies by region. Economic growth is safer at 1.5 than at 2 degrees. The Tropics and Global South are at more risk economically at 1.5 degrees and even more at 2 degrees. There’ll be multiplication of threats across the food, energy and water sectors in the continents of Asia and Africa.

Adaptation is already happening at various scales in different places, and adaptation needs are lower at 1.5 degrees than at 2. Keeping it at the lower threshold gives communities, countries and ecosystems more time, space and the ability to galvanize resources and adapt. However at 2 degrees, adaptation is more challenging for food, health sectors and ecosystems. Also, the limits to adaptation increase at 2 degrees based on individual sectors.

Majority of emission pathways with zero to little overshoot of 1.5 degrees show a decline of carbon emissions by 45% by 2030 compared to 2010 levels attaining net zero by 2030. Those that model 2 degrees threshold show a 25% cut in carbon emissions by 2030 reaching net zero in 2070. Non-CO2 emissions show similar drops in both scenarios.

Scenarios that stabilize warming at 1.5 degrees or exceed it slightly involve a vast and different array of mitigation actions for example; lowering energy and resource intensity, rate of decarbonization and reliance on carbon dioxide removal. Such pathways show cuts in methane and black carbon emissions by 35%, and cutbacks in cooling aerosols as well. Non-CO2 emission cuts can be achieved by concentrating action in the energy sector while nitrous oxide and methane from agriculture and waste sectors can be reduced. This happens for black carbon in some cases and hydrofluorocarbons. Such pathways result to better human health because of upgraded and enhanced air quality.

The carbon budget this century (amount of emissions left) for reaching 1.5 degrees is rapidly dwindling and is especially under threat from future permafrost thaw (melting of frozen soil in the poles) and emissions of methane from wetlands. As for some types of solar radiation modification e.g. placing mirrors in space, there’s a huge level of uncertainty, problems with governance and social acceptability and knowledge gaps.

Paths keeping warming to 1.5 degrees with little or no overshoot need ‘rapid and far-reaching transitions in energy, land, urban, infrastructure (transport, buildings), and industrial systems.’ The historic scale at which this needs to be done has never occurred before (is unprecedented) but the speed required has been observed before in various sectors. Such pathways need more swift, quicker and highly evident changes over the following twenty years (2 decades), in comparison to 2 degrees pathways.

At 1.5 degrees, the energy sector needs energy efficiency, electrification and low emissions energy to vastly increase in share than at 2 degrees. Clean energy (renewables) will generate 70-85% of electricity at 2050, while nuclear and fossil fuels with CCS (carbon capture and storage) also increase in usage. Deployment of CCS enables more use of natural gas but coal use diminishes to zero percent depending on a host of factors including national circumstances.

For 1.5 degrees in industry, by 2050, emissions of carbon are cut by 65-90% compared to 2010 levels but for the 2 degrees threshold this figure is 50-80%. For 1.5 degrees, a variety of new and existing methods need to be employed. Such include electrification, ‘sustainable bio-based feeds’, product substitution, and CCUS (carbon capture utilization and storage). All this depends of technical, human capacity, economic, institutional, financial and other constraints. Resource intensity and energy use change in this sector are not enough by themselves to keep warming to 1.5 degrees.

About land use, at 1.5 degrees, changes are necessary in urban planning and cuts in emissions in transport and buildings. Buildings need to be electrified more (55-75% by 2050 for 1.5 degrees; 50-70% by 2050 for2 degrees). The share of low emissions energy in the transport sector needs to be 35-65% for the 1.5 pathway and 25-45% for the 2 degrees pathway. All this is however subject to different factors and circumstances.

Furthermore, in land use, about 4 million square kilometers of land under food crops and pasture needs to be converted to forest land and energy crops. However this might be a problem given that land is also needed for human settlement, urban growth, nature etc. The planet will have to pivot toward a more plant based diet, better farming methods, and less use of resources and agrochemicals.

Now, all 1.5 degrees pathways with little overshoot need CDR (carbon dioxide removal) of a hundred to thousands gigatonnes of carbon dioxide during and up to the end of the century (2100). CDR would remove remaining emissions and absorb even more from the atmosphere making the balance net negative. This is in order to bring back temperatures to 1.5 after they exceed and peak.

CDR in this case refers to afforestation, reforestation, soil carbon sequestration, net negative technologies (BECCS, DACCS), enhanced weathering and ocean alkanization. All these remove carbon from the air. Currently it is BECCS and AFOLU (afforestation and land use) that are most covered for CDR. However the two are in direct competition with other important land uses.

All emission trajectories that overshoot 1.5 degrees require extensive CDR to return warming to 1.5 before century end.

Restoration of ecosystems and soil carbon sequestration have multiple other advantages for the human world and natural systems. They will require concerted and cohesive governance to implement.

Now, all NDCs (nationally determined contributions) submitted up until point of publication are insufficient to limit warming to 1.5. In fact, these climate plans would result to a rise of 3 degrees by century end (2100). Another thing is that pre-2030 reductions in emissions are vital to keep 1.5 degrees alive and not exceed it. The report states emissions need to be cut by 40-50% by 2010 levels.

Overshooting this target, very extensive CDR will be required to reverse warming and this still might be quite difficult, take a long time and not sufficient.

Now, if adaptation is well thought out and implemented based on particular circumstances (e.g. of a nation or community), it can aid poverty reduction and ameliorate sustainable development (synergies). The two are worsened by exceeding the 1.5 degrees threshold. Mitigation and adaptation can be cheaper when implemented in light of sustainable development.

But benefits of adaptation at 1.5 degrees work well with (synergies) and promote the SDG goals on health, poverty reduction, clean energy, cities and communities, gender, oceans and responsible consumption.

Some pathways to 1.5 degrees however can negatively affect (tradeoffs) poverty, water access and energy supply. This is when mitigation and adaptation are not considered hand in hand with sustainable development which requires social equity, environmental safety and economic growth.

Mitigation needed for 1.5 degrees can negatively affect development in countries reliant on fossil fuels for economic growth. Some types e.g. AFOLU and BECCS, affect agriculture, ecosystems, human settlement and water use because of its land requirements.

For the 1.5 degrees goal to be met, there need to be increased investment and additional financial resources (private or public, innovative finance models) for mitigation and adaptation.

Policy, technology, education, awareness creation, involvement of indigenous groups, all levels of government, local communities and especially non-state actors like community groups and faith organizations is vital.

Partnerships internationally and collective action from all stakeholders, business entities, civil society, and private sector is needed to make achievement of this goal a reality.