A greenhouse is a physical structure that allows solar radiation to enter and be absorbed by its contents while preventing the resulting heat from escaping. This mechanism creates a controlled environment that can enhances crop yields. Similarly, greenhouse gases (GHGs)—including carbon dioxide (CO2), methane (CH4), nitrous oxide (N2O), sulfur hexafluoride (SF6), water vapor, and chlorofluorocarbons (CFCs)—absorb and trap heat emitted from the Earth's surface within the atmosphere [1,2]. The majority of these emissions derive directly from human activity. According to the Intergovernmental Panel on Climate Change (IPCC) Sixth Assessment Report, electricity and heat production from burning fossil fuels are the largest global sources of emissions.
While water vapor is the most abundant GHG, its atmospheric concentration is regulated by natural precipitation cycles rather than human activity [3]. It possesses a low Global Warming Potential (GWP) of -0.001 to 0.0005 over a 100-year timescale and acts as a feedback mechanism rather than a primary forcing agent [4,5]. Similarly, while CFCs and SF6 have exceptionally high GWPs, they occur at low atmospheric concentrations and are strictly regulated by international frameworks such as the 1987 Montreal Protocol [6–8].
Consequently, environmental policy primarily focuses on three high-volume, anthropogenic gases:
· Carbon Dioxide (CO2): Holding a baseline GWP of 1, CO2 accounts for 76% of human-caused emissions (excluding water vapor) [9,10]. It persists in the climate system for hundreds to thousands of years, cycling between land, oceans, and the atmosphere [11]. Its primary drivers are fossil fuel combustion for energy and transport, alongside land-use and land-cover changes (LULC), which account for roughly one-third of CO2 emissions [12,13].
· Methane (CH4): Contributing 16% of global emissions, CH4 has a 100-year GWP of 28–36 and an atmospheric lifespan of roughly 12 years [9,14]. It is primarily generated by livestock agriculture, landfills, industry, and LULC changes [15].
· Nitrous Oxide (N2O): Making up 6% of global emissions, N2O possesses a GWP of approximately 300 and persists for over a century [9,16,17]. While naturally present via the nitrogen cycle, 40% of emissions are anthropogenic, stemming from agriculture, fuel combustion, wastewater management, and industrial processes [18–20].
Global GHG emissions continue to rise, particularly within the industrial and transportation sectors. Industry emissions stem from fossil fuel combustion and chemical transformation processes, while transportation—which relies on petroleum for 95% of its energy—accounts for roughly 15% of global emissions. This trajectory is driven by rising manufacturing demands, longer travel distances, and a consumer trend toward larger, heavier vehicles [21].
A region's carbon footprint depends on its economic development, energy mix, population density, natural resources, and local climate policies [22].
Table 1: Variation in Greenhouse Gas according to source/sector [23]
Country/Region
Major GHG Emission Sectors
Context and Trends
East Asia and Pacific
Energy (79%), Industry (8.8%), Agriculture (7.1%)
China is the leading global emitter due to rapid economic growth since the 1990s; currently expanding renewables to hit carbon neutrality by 2060 A.D. [24].
United States
Transportation (28%), Electric Power (25%), Industry (23%)
Highest cumulative historical emissions and top per-capita emitter [25].
European Union
Energy (83%), Agriculture (12%), Industry (5.2%)
Steadily reducing emissions via strict regulations and the LULUCF framework, which uses sustainable forestry and peatland restoration to capture carbon [26].
Sub-Saharan Africa
Land Use Change/Forestry (37%), Energy (29%), Agriculture (26%)
Driven by population growth and poor farming practices that convert forests to degraded croplands [27,28].
South Asia
Energy (67%), Agriculture (25%), Industry (5%)
In emerging economies such as India, experiencing sharp emission increases tied to rapid industrialization and urbanization [29].
Australia
Energy (82%), Agriculture (9.4%), Industry (6.4%)
Drop in emission due to surge in renewable energy and battery storage. [30]
Rising global temperatures increase surface evaporation and atmospheric water-holding capacity (roughly 7% per 1°C of warming). However, global precipitation shifts will be highly uneven, accentuating a "wet gets wetter, dry gets drier" pattern across mid- and high-latitude zones [31].
The IPCC projects precipitation increases at the poles and the equatorial Pacific Ocean. Conversely, sharp declines are expected in the Mediterranean (a 20% reduction), South Africa, Western Australia, Chile, and Central America (a 10% reduction). In the United States, the Fourth National Climate Assessment projects drying trends in the West and South, contrasted by increased rainfall in the North and East. Furthermore, large urban centers modify regional microclimates; by altering airflow, changing surface terrain textures, and releasing aerosols, cities induce higher condensation and localized rainfall relative to adjacent rural areas [32].
Socio-Economic and Political Vulnerabilities
Urban centers face severe flash flooding risks due to high percentages of impervious surfaces. Legacy stormwater infrastructure, designed around historical baselines, is increasingly overwhelmed by intensifying storms [33]. In arid regions, reduced rainfall threatens municipal, agricultural, and industrial water supplies. Where flooding does occur, it routinely contaminates existing clean water systems, compounding public health risks [34]. Additionally, heavy downpours trigger landslides and erosion, causing severe damage to critical infrastructure like roads and bridges.
Climate change acts as a risk multiplier that erodes state capacity by straining access to basic resources [35]. Resulting food and water insecurities historically provoke civil unrest and resource-driven conflicts, forcing mass migrations. The economic toll of these disasters is immense; for context, the United States spent $747 billion over a single five-year period on climate disaster responses. Developing nations rarely possess the financial cushion to absorb these macroeconomic shocks or fund necessary adaptation strategies.
Climate change disproportionately harms vulnerable demographics, including indigenous populations, ethnic minorities, and low-income communities across Central Africa, South/East Asia, and Central America. Indigenous peoples face cultural erasure and displacement due to their deep reliance on local ecosystems. Furthermore, distinct gender-based vulnerabilities exist. In regions lacking piped infrastructure, women and young girls carry the responsibility of gathering household water and fuel. As local sources dry up, they must travel longer distances, which exponentially raises their risk of experiencing sexual violence. This intensified domestic burden simultaneously bars women from the formal labor market and forces young girls to drop out of school [36].
Because climate change is a transboundary crisis, mitigating its effects requires sustained international collaboration [37]. Political instability and shifting domestic regimes threaten this cooperation. For instance, temporary U.S. withdrawals from the Paris Agreement undermine global policy continuity, disproportionately exposing poorer nations to risk and weakening institutional trust.
Public Health and Ecosystem Disruptions
Global health models forecast severe disruptions driven by infectious disease vectors, malnutrition, and heat stress, with North America, the Arctic, and Africa projected to experience the sharpest impacts. Warmer, wetter conditions expand the geographical range and lifecycle speed of vectors carrying pathogens like malaria and dengue fever. Furthermore, significant mental health strains and forced displacement are expected to rise across Asia, Europe, North America, and the Arctic.
On land, warming temperatures are actively shifting climate zones. In the United States, deciduous forests are migrating northward, while montane species are climbing higher in elevation to find suitable thermal zones. Such shifts compromise ecosystem structures, driving localized extinctions and introducing invasive species.
Concurrently, climate change alters animal and plant phenology—the timing of recurring biological life cycle phases. While freshwater ecosystems often exhibit delayed phenological events, terrestrial and marine systems are experiencing advanced timing. These uneven shifts create ecological mismatches, severing vital symbiotic relationships between interdependent species (such as insects emerging outside of plant flowering windows).
Livestock Dynamics
Animal agriculture is a prominent source of anthropogenic GHGs, with beef production generating the highest volumes of enteric methane (CH4). Climate change strains livestock both directly and indirectly:
· Indirect Impacts (Feed and Nutrition): Climatic shifts lower both the volume and nutritional quality of forage and feed grains. Warmer temperatures alter the carbon-to-nitrogen (C:N) ratio of crops, reducing their nutritional density. This forcing requires livestock producers to import feed at a higher financial cost—an issue acutely felt in vulnerable African agricultural sectors. Furthermore, poor-quality diets cause animals to emit higher volumes of enteric methane, establishing a destructive feedback loop.
· Direct Impacts (Physiology and Vector Pressures): Most livestock species operate within narrow thermal comfort zones. While adult sheep can tolerate a 23°C variance, younger animals like piglets, lambs, and chickens have a strict 1°C tolerance window. Deviations cause heat or cold stress, requiring supplemental energy expenses for climate-controlled housing. Chronic thermal stress degrades immune responses, lowers reproduction rates, decreases summer milk yields, and stunts meat-weight gains. Additionally, milder winters increase the survival rates and geographical range of disease-carrying insects [38].
Crop Production Dynamics
Climate change introduces both direct and indirect challenges that degrade crop quality and overall yields:
· Direct Heat and Drought Stress: Short periods of intense heat are highly destructive during key reproductive phases. Extreme heat immediately before or during anthesis (flowering) reduces pollen viability and disrupts fertilization. Drought stress during flowering reduces the overall grain count, while heat stress during the rapid grain-filling stage severely limits final grain weight. Consequently, as daily temperatures rise, the harvest index for major crops drops sharply. In wheat, every 1°C increase in temperature reduces yields by up to 6%. Furthermore, warmer nights increase plant respiration rates, consuming carbon that would otherwise go toward grain filling, lowering crop quality and yield in staples like rice. Heat stress also shortens the natural growing cycle, limiting overall plant biomass production.
· The Carbon Dioxide Paradox: While elevated atmospheric CO2 can theoretically stimulate photosynthesis, this benefit is typically lost when accompanied by higher temperatures. Controlled crop research demonstrates that for vital staples like grain sorghum, final seed yields decline when elevated CO2 is paired with rising temperatures, resulting in a net negative impact on global food security.
· Indirect Environmental Shocks: Changing precipitation patterns and shifting ocean cycles can trigger massive ecological crises, such as the 2018–2019 locust outbreaks in Africa, where climate-driven cyclones allowed pests to multiply and migrate across borders, threatening millions with hunger. Rising temperatures and humidity have also accelerated the spread of devastating diseases like coffee rust across high-altitude regions in Central and Latin America and East Africa. Additionally, intense downpours drive severe soil erosion and nutrient depletion, while rising temperatures dry out tilled soils, leaving them highly vulnerable to wind degradation. Agricultural water supplies are also under threat as drying groundwater networks cripple irrigation, forcing regions like Nepal to drill deeper wells and build protective river embankments. Meanwhile, low-lying coastal areas, such as Southeast Asian rice farms, face severe yield drops due to saltwater intrusion.
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**Some data and information are taken from notes gathered from the AGRON 695 course by the author.