International Journal of Environment and Climate Change

Global warming is often presented as a change in global mean surface temperature, yet its causes, consequences and uncertainties emerge from a coupled Earth system in which the atmosphere, ocean, cryosphere, land and biosphere exchange energy and carbon across widely different timescales. This critical narrative review synthesises evidence from palaeoclimate archives, instrumental observations, Earth-energy inventories, carbon-cycle assessments, attribution studies and process-based modelling to evaluate what is robustly known, where uncertainty remains consequential, and how past climates inform interpretation of present warming without serving as simple analogues. The evidence converges on a physically coherent picture: sustained anthropogenic greenhouse-gas forcing is the dominant cause of contemporary global warming, while aerosols, natural forcing and internal variability modulate its rate and spatial expression. Ocean heat uptake and the positive Earth energy imbalance demonstrate continuing planetary heat accumulation even when surface warming fluctuates from year to year. Fast feedbacks involving water vapour, lapse rate, clouds and surface albedo determine much of the transient-to-centennial response, whereas carbon-cycle, ice-sheet, vegetation and other slow feedbacks increasingly matter on longer horizons. The largest residual physical uncertainties concern aerosol forcing, cloud feedback, the evolution of sea-surface-temperature patterns, carbon-cycle sensitivity and nonlinear changes in major Earth-system components. These uncertainties are asymmetrical: they widen the range of plausible magnitudes and regional outcomes but do not materially weaken attribution of the observed long-term warming trend. Palaeoclimate evidence strengthens inference about climate sensitivity and state dependence, while also showing that boundary conditions and forcing histories limit direct analogy with the modern industrial perturbation. A defensible interpretation therefore combines multiple independent lines of evidence rather than privileging any single temperature record, model ensemble or historical interval. Future progress depends on sustained global observing systems, improved process representation, tighter forcing constraints, better treatment of model dependence and structured integration of palaeoclimate, observations and mechanistic theory.