Weaver was born in Victoria, British Columbia, and graduated from Oak Bay High School in 1979. He received a BSc in mathematics and physics from the University of Victoria in 1983, a Certificate of Advanced Study in mathematics from the University of Cambridge in 1984, and a PhD in applied mathematics from the University of British Columbia in 1987. After finishing his PhD, Weaver worked as a postdoctoral fellow in the School of Mathematics at the University of New South Wales in Australia in 1988, and in the Joint Institute for the Study of the Atmosphere and Ocean at the University of Washington in Seattle in 1989. Prior to joining the University of Victoria in 1992, he spent three years as an assistant professor in the department of Atmospheric and Oceanic Sciences at McGill University. Weaver is a professor and, prior to his election to the BC Legislature, was the Canada Research Chair in climate modelling and analysis in the School of Earth and Ocean Sciences at the University of Victoria, where he has worked for 25 years. He was the Lansdowne Professor until 2017. Weaver has chaired or served as a member of numerous local, national and international committees. From 2003 to 2004, he was president of the Victoria Confederation of Parent Advisory Councils. In 2004–2005 he was president of the University of Victoria Faculty Association and served as their chief negotiator in the 2003 and 2006 collective bargaining. Weaver has been engaged in public outreach and science communication. He sat on the CRD Roundtable on the Environment, and has delivered numerous public and school presentations and hosted many school field trips to his university laboratory over his career. He continues to lead the development of the Vancouver Island School Based weather station project. Weaver has authored or coauthored over 200 peer-reviewed papers in climate, meteorology, oceanography, earth science, policy, education and anthropology journals. He was a lead author in the United Nations Intergovernmental Panel on Climate Change2nd, 3rd, 4th and 5th scientific assessments. He was the chief editor of the Journal of Climate from 2005 to 2009.
His book, Keeping our Cool: Canada in a Warming World was published by Viking Canada in September 2008. His second book, Generation Us: The Challenge of Global Warming was published by Raven Books in 2011.
Politics
Weaver joined the British Columbia Green Party in October 2012 as the party's deputy leader and candidate for the riding of Oak Bay-Gordon Head. He was elected in the 2013 provincial election as the first Green Party MLA in British Columbia's history. Since his running for office, Weaver has been a strong supporter of the development of the clean technology industry and a firm critic of the LNG Canada project. Weaver calls the LNG plan a "pipe-dream", asserting that Liberal government promises of a $1 trillion boost to the provincial GDP, a $100 billion prosperity fund, and the elimination of the provincial debt and sales tax are unsubstantiated and irresponsible. Weaver has also been involved in several local issues, most recently calling for a reconsideration of the Capital Regional District's sewage treatment plan in 2013. In August 2013, Weaver chose not to take on leadership of the BC Green Party stating: "I have an ambitious agenda for my term as MLA and achieving this requires focus and hard work. I consider it in the best interests of my constituents, the party and the province if, for now, I focus on my role as MLA and support a new interim leader who can concentrate on building the party." However, Weaver also stated that if he decided to re-run in the 2017 provincial election and was still the only elected BC Green Party MLA, he would then seek leadership of the party. On 24 November 2015 Weaver announced his bid to run for leader of the British Columbia Green Party. He was acclaimed to this position on December 9, 2015. In the 2017 election, Weaver was reelected and the BC Green Party increased their share of the popular vote to 16.8% from 8.13%. Weaver was joined by BC Green MLAs Sonia Furstenau and Adam Olsen, forming the first BC Green Caucus in the province's history. The election ended in a minority government, with the Greens holding the balance of power. Weaver led the subsequent negotiations with the BC Liberal Party and BC NDP. The Greens ultimately opted to remain an opposition party rather than forming a formal coalition and signed a Confidence and Supply Agreement with the BC NDP. The Agreement commits Weaver, Furstenau and Olsen to vote with the BC NDP government in matters of confidence, such as provincial budgets, and commits both parties to implementing a number of shared policy priorities. In October 2019, Weaver announced that, due to a family health issue, he would step down as Green Party leader once another leader had been chosen and that he would not seek re-election to the Legislative Assembly. Adam Olsen became interim leader effective January 6, 2020. Weaver later announced that he was leaving the leadership, and the Green caucus, effective January 20, 2020, before a new leader could be elected, citing the need to "attend to personal matters". He now sits as an independent.
Lawsuit over ''National Post'' articles
The British Columbia Supreme Court ruled that Weaver had been libelled in a series of National Post articles written by Terence Corcoran, Peter Foster and Kevin Libin that accused him of scientific misconduct in his studies of climate change, among other claims. In Weaver v. Corcoran the court ruled that the charges were false and that "the defamation in this case was serious. It offended Dr. Weaver's character and the defendants refused to publish a retraction". The court awarded Weaver $50,000 in damages, ordered that the offending articles be removed from the newspaper's archives and that a complete retraction be published. The National Post appealed the decision. On April 21, 2017, the British Columbia Court of Appeal ordered a retrial in the defamation suit, citing an error in the judge's analysis of the articles pertaining to the suit.
Documentary film
Weaver is featured in the documentary film Running on Climate. Filming began before Weaver was nominated as a candidate and continued through the 2013 election campaign.
