12.4 Mitigation and adaptation strategies for climate change

Mitigation Strategies

Climate change mitigation and adaptation are two complementary approaches to dealing with global warming. Mitigation aims to reduce or prevent greenhouse gas emissions so the problem doesn't get worse. Adaptation focuses on adjusting to the climate changes already underway or expected in the future. Both are necessary because even aggressive emission cuts can't undo warming that's already locked in.

International frameworks like the Paris Agreement coordinate these efforts globally, while the IPCC synthesizes the science behind them. Effective climate action requires policy, technology, and behavioral change at every scale.

Reducing Greenhouse Gas Emissions

The core of mitigation is cutting the amount of greenhouse gases entering the atmosphere. This happens across three major sectors:

Energy production is the largest source of emissions, so switching to low-carbon sources has the biggest impact.

• Solar, wind, hydro, and geothermal power generate electricity without releasing $CO_2$ during operation
• Biofuels derived from plant materials (corn, sugarcane) can substitute for gasoline and diesel in transportation, though their net carbon benefit depends on how the feedstock is grown and processed

Energy efficiency reduces total energy demand, which means fewer emissions even before the grid is fully decarbonized.

• Improved insulation, LED lighting, and ENERGY STAR appliances lower electricity consumption in buildings
• Fuel-efficient vehicles (hybrids, battery-electric cars) and expanded public transit cut emissions from transportation, which accounts for roughly 28% of U.S. greenhouse gas emissions

Sustainable agriculture targets the significant emissions that come from food production.

• Reduced tillage and cover cropping sequester carbon directly in soils
• Precision fertilizer application and slow-release formulas decrease nitrous oxide ($N_2O$) emissions, a greenhouse gas about 273 times more potent than $CO_2$ over a 100-year period
• Anaerobic digesters capture methane ($CH_4$) from livestock waste and convert it into usable biogas

Enhancing Carbon Sinks

Beyond reducing emissions, mitigation also involves pulling $CO_2$ out of the atmosphere and locking it away. These approaches are called carbon sequestration.

• Afforestation and reforestation increase carbon uptake by establishing new forests or restoring degraded ones. Growing trees absorb $CO_2$ through photosynthesis and store it as biomass.
• Soil carbon sequestration enhances the carbon stored in agricultural soils through no-till farming and adding organic amendments like compost or biochar
• Carbon capture and storage (CCS) captures $CO_2$ at the point of emission (power plants, cement factories) and injects it into deep underground geological formations for long-term storage

Emissions trading systems (cap-and-trade) create economic incentives that complement these technical approaches. Here's how they work:

1. A government or regulatory body sets a total cap on emissions for a sector or region.
2. That cap is divided into individual allowances, each permitting a set amount of emissions.
3. Companies that emit less than their allowance can sell their surplus to companies that exceed theirs.
4. Over time, the cap is lowered, tightening the overall emissions budget and driving further reductions.

The European Union Emissions Trading System (EU ETS) is the world's largest, and the Regional Greenhouse Gas Initiative (RGGI) operates among northeastern U.S. states.

Adaptation Measures

Building Resilience to Climate Impacts

Some degree of climate change is already unavoidable due to past emissions. Climate resilience means preparing communities and ecosystems to withstand these impacts.

• Early warning systems and evacuation plans for extreme weather events like hurricanes, heat waves, and floods save lives when disasters strike
• Flood defenses such as seawalls, levees, and elevated buildings protect coastal areas from sea-level rise. Miami, for example, has invested billions in stormwater pumps and raised roads.
• Agricultural adaptation includes diversifying crop varieties to tolerate heat and drought, shifting planting seasons, and expanding irrigation infrastructure

Green infrastructure uses natural systems to buffer climate impacts in urban areas:

• Urban green spaces (parks, green roofs) reduce the urban heat island effect, where cities can be 1–3°C warmer than surrounding rural areas, and they absorb stormwater runoff
• Permeable pavements allow rainwater to infiltrate the ground, reducing flood risk and recharging groundwater supplies
• Constructed wetlands filter pollutants, provide wildlife habitat, and store excess floodwater

Exploring Geoengineering Options

Geoengineering refers to large-scale, deliberate interventions designed to counteract climate change. These approaches remain largely theoretical and controversial because of uncertain side effects and governance challenges. They fall into two categories:

Solar radiation management (SRM) aims to reflect more sunlight back into space to cool the planet.

• Stratospheric aerosol injection would release reflective sulfate particles into the upper atmosphere, mimicking the temporary cooling observed after large volcanic eruptions like Mount Pinatubo (1991)
• Marine cloud brightening proposes spraying fine seawater droplets to make low-lying clouds more reflective, increasing their albedo

Carbon dioxide removal (CDR) seeks to extract $CO_2$ directly from the atmosphere.

• Ocean iron fertilization would add iron to ocean surface waters to stimulate phytoplankton blooms that absorb $CO_2$, but risks disrupting marine food webs
• Direct air capture (DAC) uses chemical filters to pull $CO_2$ from ambient air. It works, but current costs are high (roughly $400–600 per ton of $CO_2$) and the process is energy-intensive.

A key concern with all geoengineering: SRM techniques don't actually remove greenhouse gases, so they only mask symptoms. If SRM were ever stopped abruptly, temperatures could spike rapidly. CDR addresses the root cause but can't yet operate at the scale needed.

International Efforts

Global Agreements and Targets

The Paris Agreement, adopted in 2015 under the United Nations Framework Convention on Climate Change (UNFCCC), is the central international framework for climate action. Its core goal is limiting global warming to well below 2°C above pre-industrial levels, with an aspirational target of 1.5°C.

How it works:

1. Each country submits nationally determined contributions (NDCs) outlining its specific emission reduction targets and planned climate actions.
2. NDCs are updated every five years, with the expectation that each round will be more ambitious than the last.
3. Global stocktakes assess collective progress toward the agreement's goals and inform the next round of NDCs.
4. The agreement includes provisions for climate finance to help developing nations fund mitigation and adaptation, recognizing that wealthier nations bear greater historical responsibility for emissions.

Climate policy operates at multiple levels simultaneously:

• National governments set emission reduction goals, implement carbon pricing (carbon taxes or cap-and-trade), and fund clean energy research
• Subnational actors like states and cities develop their own climate action plans, including renewable portfolio standards and updated building codes
• International organizations such as the World Bank and the Green Climate Fund provide funding and technical support for climate projects in developing countries

Scientific Assessment and Guidance

The Intergovernmental Panel on Climate Change (IPCC) is the leading international body for evaluating climate science. It doesn't conduct original research. Instead, thousands of scientists worldwide volunteer to review and synthesize the existing literature into comprehensive assessment reports, released every 5–7 years.

These reports cover three main areas:

• The physical science basis of climate change (how the climate system works and how it's changing)
• Impacts, adaptation, and vulnerability (what climate change means for ecosystems and human societies)
• Mitigation (what can be done to reduce emissions)

The IPCC also publishes special reports on focused topics. Its 2018 special report on 1.5°C of warming was particularly influential, showing that the difference between 1.5°C and 2°C of warming carries significant consequences for coral reefs, sea-level rise, and extreme heat. Policymakers rely on IPCC findings to set targets and design climate strategies.