In the face of global environmental concerns, legal institutions must cultivate a reflexive capacity to monitor global ecological shifts and to reconfigure their practices accordingly. But, it remains unclear whether harder or softer legal norms are more capable of enhancing such ecological reflexivity. This article traces variations in harder and softer norms in two aspects of the evolution of the global climate change regime-national contributions to mitigation and review mechanisms- A nd their implications for ecological reflexivity. We find the regime's reflexivity has increased moderately and slowly over time but without a consistent shift towards harder or softer norms. The Paris Agreement's innovative approach, combining harder procedural commitments with softer substantive provisions (a 'crème brûleé'), has potential to encourage flexible responses to changing conditions within a stable, long-term architecture. However, the Agreement's softer, transparency-based compliance framework provides limited assurance that countries will make and fulfill ambitious commitments.