Health care is a carbon-intensive industry; in the UK, it is the largest contributor of greenhouse gases in the public sector and has a carbon footprint larger than that of some medium-sized European countries The single largest component of the carbon footprint of mental health care is pharmaceuticals, followed by medical equipment and clinically related travel. Psychiatrists need to engage in designing and implementing less carbon-intensive care pathways. The Lancet Commission and WHO have both stated that climate change is the largest threat to human health in the 21st century. This threat extends to mental illness, with increasing evidence that unstable weather patterns—a direct consequence of climate change—can have harmful effects on mental health. Limiting the environmental effects of mental health care are crucial to the sustainability of mental health care, both in the UK and worldwide.