Piers is an atmospheric physicist who moved to Leeds in 2005. He researchers both the causes of climate change and climate feedbacks in the Earth system, to understand temperture and rainfall changes and improve their projections. This is used to inform both climate impacts and mitigation strategies. He has played a significant role authoring Intergovernmental Panel on Climate Change (IPCC) reports, including the Fourth (2007) and Fifth (2013) and Sixth (2021) assessment reports and the IPCC Special Rreport on 1.5°C (2018).

He was awarded a Royal Society Wolfson Merit Award for 2011-2016. He was made a Fellow of the American Geophysical Union in 2019. He is a Web of Science Clarivate Analytics highly cited researcher.

As well as his research career, he established the forest protection and research charity: the United Bank of Carbon and has a number of roles advising industry and government, including membership of the Rolls Royce Environment Advisory Board and the UK Commitee on Climate Change.