Designing policy for climate change requires analyses which integrate the interrelationshipbetween the economy and the environment. We argue that, despite their dominance in theeconomics literature and influence in public discussion and policymaking, the methodologyemployed by Integrated Assessment Models (IAMs) rests on flawed foundations, which becomeparticularly relevant in relation to the realities of the immense risks and challenges of climatechange, and the radical changes in our economies that a sound and effective response require. Weidentify a set of critical methodological problems with the IAMs which limit their usefulness anddiscuss the analytic foundations of an alternative approach that is more capable of providinginsights into how best to manage the transition to net-zero emissions