A professor of atmospheric physics at Oxford, former Chief Executive at the Met Office, and founder of the Hadley Centre, he is a venerable proponent who was the lead editor of the first three IPCC reports. Here's an example quote:
“As a climate scientist who has worked on this issue for several decades, first as head of the Met Office, and then as co-chair of scientific assessment for the UN intergovernmental panel on climate change, the impacts of global warming are such that I have no hesitation in describing it as a weapon of mass destruction."
Is he an alarmist?
The conspiracy theory school of climate skepticism portrays him as someone who spreads scary stories to frighten small children. For example, in a November 2006 article in Australia's The Daily Telegraph, journalist Piers Akerman quoted Houghton as saying "Unless we announce disasters, no one will listen." He attributed this quote to Houghton's 1994 book Global Warming, The Complete Briefing. However, the quote does not appear in any edition of the book and Houghton denies saying it.
On the looming disaster
(Lecture) On the history global warming science