Climate Change

India's approach to climate change centres on adaptation as the primary focus, with specific mitigation commitments. India recognises its historical low emissions and argues for equitable burden-sharing, while also demonstrating voluntary actions through the National Action Plan on Climate Change (NAPCC) and its eight missions.

Ozone (O₃) is an allotrope of oxygen with three atoms. It exists in two forms: - **Tropospheric ozone:** "bad ozone" — ground-level pollutant; contributes to smog; harmful to breathe - **Stratospheric ozone:** "good ozone" — absorbs UV radiation, especially UV-B; protects life on Earth The ozone layer has been depleted primarily by chlorofluorocarbons (CFCs) and other halogenated compounds through catalytic reactions.

Climate change causes a cascade of environmental impacts — from melting ice caps to shifting disease vectors. UPSC tests both global impacts and India-specific observations. Key distinction: climate (long-term average) vs weather (short-term); climate change = measurable shifts in temperature, rainfall, snow, and wind patterns over decades.

The Paris Agreement is an international treaty on climate change, signed in 2016, covering climate change mitigation, adaptation, and finance. Negotiated by 196 parties at the 2015 United Nations Climate Change Conference (COP21) near Paris, it provides the foundational framework for global climate action in the 21st century. A primary goal of the agreement is to limit the rise in global average temperature to well below 2 °C above pre-industrial levels, with an ambitious pursuit of limiting it to 1.5 °C. For UPSC Prelims, understanding this temperature target, the bottom-up approach of Nationally Determined Contributions (NDCs), and its distinction from the Kyoto Protocol is crucial for grasping international environmental governance and India's commitments.

The Social Cost of Carbon (SCC) is an economic estimate, typically expressed in dollars per ton, of the total monetary damages associated with emitting one additional ton of carbon dioxide into the atmosphere. It quantifies the long-term economic harm from climate change, encompassing diverse impacts such as agricultural losses, adverse health effects, infrastructure damage from sea-level rise, and degradation of ecosystem services. For UPSC Prelims, understanding the SCC is crucial as it provides policymakers with a vital tool for cost-benefit analyses of climate policies, informing regulatory impact assessments, and guiding investment decisions related to greenhouse gas emissions. By translating the environmental impact of carbon into tangible economic terms, it helps governments make evidence-based decisions for climate action and sustainable development.

Ocean Acidification is the ongoing change in ocean chemistry, characterized by the lowering of ocean pH, driven by the absorption of atmospheric carbon compounds. The ocean acts as a significant reservoir, absorbing about one-third of the CO2 produced by human activities. As this uptake increases, it surpasses the ocean's natural buffering capacity, leading to an increase in hydrogen ion concentration, a decrease in carbonate ion concentration, and a reduction in pH, making the oceans less alkaline. The primary ecological impact of acidification is on marine calcifying organisms, such as corals, molluscs, and some plankton. These organisms rely on carbonate ions to build their calcium carbonate shells and skeletons. The reduced availability of these ions makes calcification more difficult. Furthermore, acidification causes the "saturation horizon"—the depth below which calcium carbonate dissolves—to rise closer to the surface. This exposes more marine life to undersaturated water, making their shells and skeletons vulnerable to dissolution.

Solar Radiation Modification (SRM), also known as solar geoengineering or albedo modification, refers to a suite of large-scale approaches designed to reduce global warming. These methods primarily aim to increase the amount of sunlight reflected away from Earth and back into space, thereby cooling the planet. SRM is intended to complement, rather than replace, ongoing efforts to reduce greenhouse gas emissions. This concept is crucial for UPSC Prelims as it represents a potential, albeit controversial, climate change mitigation strategy alongside emission reductions and Carbon Dioxide Removal (CDR). Unlike other methods, SRM could reduce global temperatures within months of deployment. However, it does not address the root cause of climate change – atmospheric carbon dioxide concentrations – meaning issues like ocean acidification would persist. Its rapid effect and potential for unilateral deployment also raise significant governance questions.

Direct Air Capture (DAC) is an innovative technology that employs chemical or physical processes to extract carbon dioxide (CO2) directly from the ambient air. When this captured CO2 is subsequently stored safely long-term, the overall process is termed Direct Air Carbon Capture and Sequestration (DACCS), directly achieving carbon dioxide removal (CDR). Such systems are vital Negative Emissions Technologies (NETs) aimed at reducing atmospheric CO2 concentrations. Unlike traditional Carbon Capture and Storage (CCS), which captures CO2 from concentrated point sources like industrial exhaust stacks, DAC operates on diffuse atmospheric CO2. This distinction makes DAC particularly important for addressing emissions from non-stationary sources, such as airplanes or distributed emissions, which cannot be captured at source. Its potential to actively reduce global atmospheric CO2 levels makes it a significant concept for climate change mitigation efforts, particularly for achieving net-zero targets.

The Carbon Fertilization Effect describes the phenomenon where increased levels of atmospheric carbon dioxide (CO2) lead to an accelerated rate of photosynthesis and a reduction in leaf transpiration in plants. This effect varies significantly depending on factors like plant species, ambient temperature, and the availability of water and nutrients. While it can lead to an increase in Net Primary Productivity (NPP) and has been linked to a 44% rise in Gross Primary Productivity (GPP) since the 2000s, this does not consistently translate into enhanced overall plant growth or substantial long-term carbon storage in all cases. This concept is vital for UPSC Prelims as it touches upon critical aspects of climate change, the global carbon cycle, and food security. Terrestrial ecosystems, influenced by this effect, have historically absorbed CO2, partially mitigating climate change and contributing to significant global "greening" since the early 1980s. However, the capacity of this effect to significantly reduce atmospheric CO2 in the long run is limited by increasing anthropogenic emissions. Furthermore, a negative consequence is the potential reduction in the nutritional quality of essential food crops, impacting global and India's food security strategies.

Carbon dioxide (CO₂) is a primary greenhouse gas that is naturally present in the atmosphere as part of the Earth’s carbon cycle—

Carbon Capture and Storage (CCS) is a process designed to mitigate climate change by preventing carbon dioxide (CO2) from entering the atmosphere. It involves separating CO2 from large point sources, such as industrial installations or natural gas processing plants, before it is released, and then transporting it to a long-term storage location, typically deep geological formations, for isolation. This technology is often expanded to Carbon Capture, Utilization, and Storage (CCUS), where the captured CO2 is used, primarily in Enhanced Oil Recovery (EOR). For UPSC Prelims, CCS/CCUS is a critical topic under Environment and Climate Change due to its potential role in achieving emission reduction targets and net-zero goals, particularly in hard-to-abate sectors like heavy industry. Aspirants should understand its mechanism, current status, limitations, and its intersection with energy policy and other climate mitigation strategies like Bioenergy with Carbon Capture and Storage (BECCS).