Responses to climate change divide into two broad strategies: mitigation, actions that reduce or prevent greenhouse gas emissions, and adaptation, adjustments to actual or expected climate effects. Mitigation includes switching to renewable energy, electrifying transport, and improving efficiency; adaptation includes building seawalls, developing drought-resistant crops, and redesigning cities for heat. The ultimate mitigation target is net zero, balancing emissions produced with those removed from the atmosphere, with carbon neutrality specifically referring to net-zero CO₂ emissions, often achieved in part through offsets. Climate sensitivity describes how much the global average temperature rises for each doubling of atmospheric CO₂, a key parameter in climate models, and the Paris Agreement's 1.5°C target is the aspirational limit intended to avoid the worst climate impacts.
The climate system contains feedback loops that amplify or dampen change. A positive feedback accelerates warming, as when melting ice exposes darker surfaces that absorb more heat. A negative feedback slows warming, as when increased CO₂ initially stimulates some plant growth that absorbs CO₂. Tipping points are thresholds beyond which a system change becomes self-sustaining. Major tipping points include Amazon dieback, the collapse of ice sheets in Greenland and Antarctica, the slowdown of the Atlantic Meridional Overturning Circulation, and large releases of methane from thawing permafrost. Avoiding these thresholds is a central reason for the urgency of rapid emissions cuts.
When emissions cannot be eliminated quickly enough, additional tools come into play. Geoengineering refers to large-scale interventions in Earth's systems to counter climate change. Solar radiation management, one branch, aims to reflect sunlight away from Earth, for example through stratospheric aerosols. Carbon dioxide removal (CDR) instead removes CO₂ directly from the atmosphere using natural or technological methods: afforestation as CDR plants trees that sequester carbon; direct air capture (DAC) uses machines to extract CO₂ from ambient air; bioenergy with carbon capture and storage (BECCS) combines burning biomass with geological storage of the resulting CO₂; and ocean alkalinity enhancement adds alkaline materials to seawater to increase its CO₂ absorption. The drawdown concept refers to the moment when atmospheric greenhouse gas concentrations begin to fall, and Project Drawdown is a research effort cataloguing practical climate solutions.
Policy underpins many of these efforts. In the United States, the Environmental Protection Agency (EPA) enforces environmental laws, the National Environmental Policy Act (NEPA) requires environmental impact assessments for federal projects, and the Endangered Species Act protects threatened species. Internationally, CITES regulates trade in endangered species, RAMSAR protects wetlands, the 1997 Kyoto Protocol set binding emission targets for developed countries, and the 2015 Paris Agreement shifted to voluntary national contributions from all countries. Loss and damage refers to climate impacts that cannot be adapted to, and COP28's first Global Stocktake produced an agreement to transition away from fossil fuels. Nature-based Solutions (NbS), the Blue Economy of sustainable ocean use, and green hydrogen, hydrogen produced by electrolysis using renewable electricity to decarbonize sectors like steel and aviation, all play growing roles. Carbon offsets, funding emission reductions elsewhere to compensate for one's own emissions, are controversial because their quality varies; high-quality offsets must be additional, permanent, verifiable, and not double-counted. The most cost-effective actions individuals can take include voting and civic engagement, dietary shifts, transport choices, and reducing home energy use. The overall takeaway of environmental science is that human well-being is inseparable from ecological health, and addressing the intertwined crises of climate and biodiversity requires system-level changes in energy, food, economics, and governance.