<p>Carbon dioxide (<InlineEquation ID="IEq1"> <EquationSource Format="TEX">\(\mathrm {CO_2}\)</EquationSource> <EquationSource Format="MATHML"><math> <msub> <mi mathvariant="normal">CO</mi> <mn>2</mn> </msub> </math></EquationSource> </InlineEquation>) emissions resulting from hydrocarbon combustion remain one of the major contributors to global climate change, necessitating the development of mathematical models capable of describing the complex interactions between emission sources and natural carbon sequestration processes. In this study, a nonlinear lumped chemical kinetics model is developed to investigate the dynamics of atmospheric carbon dioxide generated from the combustion of kerosene, liquefied petroleum gas (LPG), petrol, and diesel, while incorporating oxygen consumption, water vapor production, photosynthesis, glucose formation, and carbonic acid formation as natural carbon removal mechanisms. The governing model consists of a system of nine coupled nonlinear ordinary differential equations derived using the law of mass action. Qualitative analysis establishes the positivity, boundedness, existence, and uniqueness of solutions, ensuring that the model is mathematically and physically well posed. A positive equilibrium point is obtained analytically and verified numerically. Local stability is investigated through Jacobian matrix analysis, and numerical evaluation confirms that all eigenvalues possess strictly negative real parts, demonstrating that the positive equilibrium is locally asymptotically stable. Numerical simulations are performed in MATLAB R2023b using the stiff solver <Emphasis FontCategory="NonProportional">ode15s</Emphasis>, and the trajectories of all state variables converge smoothly to finite equilibrium values, confirming the analytical results. A global sensitivity analysis based on Latin Hypercube Sampling (LHS) and Partial Rank Correlation Coefficients (PRCC) identifies the parameter <InlineEquation ID="IEq2"> <EquationSource Format="TEX">\(a_{6}\)</EquationSource> <EquationSource Format="MATHML"><math> <msub> <mi>a</mi> <mn>6</mn> </msub> </math></EquationSource> </InlineEquation> as the dominant factor governing the system dynamics, while bifurcation analysis with respect to the oxygen replenishment parameter <InlineEquation ID="IEq3"> <EquationSource Format="TEX">\(\beta _{O}\)</EquationSource> <EquationSource Format="MATHML"><math> <msub> <mi>β</mi> <mi>O</mi> </msub> </math></EquationSource> </InlineEquation> demonstrates smooth equilibrium behavior without qualitative changes over the investigated parameter range. The combined analytical and numerical results indicate that the proposed nonlinear lumped chemical kinetics model provides a mathematically consistent and computationally robust framework for analysing carbon dioxide emissions and evaluating the influence of natural carbon sequestration mechanisms. The model offers a useful quantitative tool for supporting future investigations on greenhouse gas mitigation, sustainable environmental management, and climate policy development.</p>