Essays on macrodynamic theory, historical time and climate change

The dissertation is organized in 3 chapters dealing with the timescale of macrodynamic growth models in the short and in the long run, as well as with the analysis of the climate-economy interplay over the business cycle. The first essay provides an analytical solution to the differential equation that regulates the motion of the neo-Kaleckian model in the short run. After presenting a simple open economy neo-Kaleckian model with government activity, the essay analytically derives an expression for the time of adjustment, defined as the time required for the system to make a $ k $ percent adjustment from one steady-state to another. The second chapter seeks to answer the question of \textit{when is the long run} in long-run growth models driven by demand. By making use of numerical integration, the essay analyses the time of adjustment from one steady-state to the other in two well-known demand-led growth models: the Sraffian Supermultiplier and the fully-adjusted version of the neo-Kaleckian model. The third chapter of the dissertation presents a business cycle model encompassing the short-run effect of mobilizing green investment to achieve longer-term climate goals. In doing so, the chapter focuses on the dynamics of green and brown investment, assessing whether the interplay between green and capital formation, on one hand, and CO2 emissions, on the other, may allow for conditions of coupling or decoupling - speeding up or slowing down the path towards net-zero emissions.