6.3 Climate change — mitigation and adaptationIB Environmental Systems and Societies HL: Revision notes

To avoid the risk of catastrophic climate change, global action is required, not measures adopted only by certain states. Decarbonisation means reducing or ending the use of energy sources that emit CO2 and replacing them with renewable sources. Costa Rica generates about 98% of its electricity from renewables, but transport still burns fossil fuels, so decarbonisation must extend to every sector.

A variety of mitigation strategies address climate change: renewable energy, energy efficiency, sustainable transport, carbon sequestration (forests, soils, wetlands), carbon capture and storage, reduced methane emissions and changes in diet or agriculture.

Adaptation strategies aim to reduce adverse effects and maximise any positive consequences. In the Mekong Delta, farmers use salt-tolerant crops and rice-shrimp rotation, and authorities replant mangroves (which absorb wave energy and provide fish nurseries) and build sluice gates.

Individuals and societies on many scales develop adaptation plans, such as National Adaptation Programmes of Action (NAPAs) and resilience and adaptation plans.

(HL) Responses may be led by governments or by non-governmental stakeholders. They include economic measures (carbon taxes, subsidies), legislation, goal-setting commitments (net zero by a date) and personal life changes.

(HL) The UN has played a key role through the UNFCCC and the Paris Agreement (2015), which aims to hold warming well below 2 °C and pursue 1.5 °C through voluntary NDCs.

(HL) The IPCC proposes a range of emissions scenarios with targets: AR6 best estimates by 2081 to 2100 are 1.8 °C (very low emissions), 2.7 °C (intermediate) and 4.4 °C (very high).

(HL) Technology is being developed to help mitigation (renewables, storage, carbon capture, direct air capture). Challenges include cost, lack of enforcement of NDCs, political and economic interests, unproven technology and public resistance.

(HL) Geoengineering is a mitigation strategy that treats the symptom, not the cause. Examples: stratospheric aerosol injection (reflecting sunlight, like Mount Pinatubo 1991, which cooled the Earth by about 0.5 °C) and carbon dioxide removal. Risks: termination shock, unintended effects on rainfall, ocean acidification continuing and governance.

(HL) A range of stakeholders (NGOs, scientists, media, businesses, youth movements) play an important role in changing perspectives. (HL) Perspectives on the necessity, practicality and urgency of action vary between individuals and societies.

(HL) The tragedy of the commons suggests that catastrophic climate change is likely unless there is international cooperation on an unprecedented scale: the atmosphere is shared, each country benefits from emitting, and the costs are shared by all.