How can we keep global warming to 1.5°C?
In a recent special report in New Scientist, Graham Lawton has sketched out what we must do to limit global warming to 1.5°C, the agreed threshold for a chance of avoiding irreversible and dangerous climate change. Quoting a lead author of the latest IPCC report on 1.5°C: " We have to do everything, and we have to do it immediately." This is not impossible, since we have the necessary technologies, but it will require unprecedented rates of transformation. The article lays out seven levels of increasing difficulty that must be pursued simultaneously.
First, some background. Setting aside agricultural carbon emissions, 48% of the remainder is to produce heat for buildings and industry, of which 27% is from renewable sources. The next 32% is for transport, with only 3% from renewables. The remaining 20% is for power generation, of which 25% is from renewable sources. Our fossil fuel emissions have already warmed the planet by 1°C, so we have to reduce net emissions to zero by mid-century. If everybody adopts a low-carbon lifestyle immediately, we can avoid overshooting the limit. Otherwise we shall need to use expensive carbon capture and storage (CCS) and unproven carbon dioxide removal (CDR) technologies to bring us back down to a safe level by 2100.
It is possible to calculate what our remaining carbon budget released to the atmosphere is to try to keep global warming to 1.5°C. Releasing 770 gigatonnes might give us a 50:50 chance of keeping to that target. If we want to raise the odds to two thirds, we should emit only 570 gigatonnes. With more pessimistic assumptions, the limit is considerably lower. Annual global carbon emissions are 40 gigatonnes. Half of that budget is already accounted for by existing and planned electricity generating plants unless we retire them early. To avoid continuing global warming, we must bring net emissions to zero. The following are all the things we must do together to succeed in that.
Kill fossil fuels. The move to renewable energy is accelerating, generating a quarter of our electricity in 2016, more than 10% of our total energy consumption, but we need almost complete decarbonization of electricity generation by 2050. Any continuing use of fossil fuels must be accompanied by carbon capture and storage (CCS).
Travel light. At present, more than 90% of our transport is powered by oil (petrol/gasoline, diesel and aviation fuel) and just 3% from renewables. A quarter of the energy-related CO2 emissions come from transport, and this is growing at 2.5% per year. Even a 30% reduction by 2030 means switching to electric vehicles (powered by renewables), improving fuel efficiency, replacing oil by biofuels including for aviation, and making personal sacrifices like using buses and trains over cars and planes, and traveling less.
Rebuild everything. Our homes, shops, offices and buildings account for 23% of energy-related emissions, mostly electricity for lighting, heating, cooling, elevators, office equipment and appliances. But one third is fossil fuels (gas) used for heating and cooking. These emissions need to be reduced by 80-90% by 2050, requiring energy-efficient lighting, insulation and double-glazed windows, and non-fossil-fuel heating and cooking systems. We need to refurbish 5% of existing buildings every year, and make all new buildings zero carbon by 2020, moving away from carbon-intensive concrete and steel to carbon-neutral wood-based materials or changing construction methods entirely.
A new industrial revolution. Industry uses coal and other fossil fuels to produce heat and steam to produce metals, pulp and paper, chemicals, concrete and minerals, and this needs to be reduced by 80%. Phasing out coal, increasing energy efficiency and electrifying would only be a beginning. We need massive R&D to find new, carbon-free industrial process for cement, iron and steel, plus carbon capture and storage for uses we cannot replace in time. Some new technologies exist, but they must become more affordable and scaled up.
Reap what we sow. Land use produces one quarter of carbon emissions, raising issues of forests, farms and food. Growing food inevitably emits CO2, and pasture with cows on it is a gigantic source of CO2 and methane. Land can be a carbon sink, and forests pull CO2 out of the air. We need to intensify agriculture while consuming less of foods with high greenhouse gas emissions, especially from cattle, swapping pasture for forests and finding room to produce biofuels for aviation. We also have to reduce deforestation.
Suck, not blow. Reaching net emissions does not mean no emissions, since some cannot be eliminated, like nitrous oxide from agricultural fertilizers. Any remaining emissions need to be balanced by removing carbon dioxide already in the atmosphere. All pathways to 1.5C require carbon dioxide removal (CDR), for which we have no proven technologies. Planting forests is the simplest way. There are proposals for bioenergy with carbon capture and storage (BECCS) where you grow biofuels, burn them, and sequester the CO2. This has not been done at scale and is a major risk in reaching the target.
Change ourselves. Addressing our demand for energy is the biggest challenge. When we use an electrical appliance, spend time inside a building, use hot water, travel anywhere in a vehicle, or buy or eat anything, we are contributing to the problem. We need to start today to make sacrifices: drive less, fly less, consume less meat, have fewer children. A plant-based diet reduces a food carbon footprint by 90%. Avoid beef with a carbon footprint three times pork and six times chicken. Tropical fruits imported by air, and cheese are other offenders. Reduce short car journeys; car-pool, bike or walk instead. But one vacation flight would wipe out the benefits of going vegetarian for a year or driving 2500 km less. In your home, replace appliances with energy-efficient models, lower the temperature of hot water, use a low-flow showerhead, do not leave appliances on standby, and dry washing outside. Smart thermostats can reduce household emissions by up to 26%. Moving to a smaller home can cut emissions by 27%. At the office, turning off lights and your workstation when leaving, and unplugging your phone charger, can cut emissions by up to 28%. Working from home in the US can mean driving 77% less.
Above all, there is a lack of political will for the biggest transformation ever. People have to demand these changes with mass movements. This may seem impossible, but we have to try. We need to convince everyone that green alternatives improve our quality of life as well as the environment.
Source: Summarized from Lawton, Graham. 2018. Hitting 1.5°C. Special Report. New Scientist Vol. 240, Issue 3207, pp. 31-37. 8 December 2018.
Last updated 24 December 2018