The new international trade secretary, Anne-Marie Trevelyan, has been accused of rejecting the science behind the climate emergency after a series of tweets came to light showing her dismissing those who believe in global heating as “fanatics”.

Labour has condemned the appointment of Trevelyan, who was elevated from junior business minister, which took in the brief of promoting clean growth, to replace Liz Truss, the new foreign secretary, as part of Boris Johnson’s reshuffle on Wednesday.

The opposition unearthed a series of tweets sent by Trevelyan between 2010 and 2012 that explicitly reject the science of global heating. “Clear evidence that the ice caps aren’t melting after all, to counter those doom-mongers and global warming fanatics,” read one.

Another, sent in support of a campaign against windfarms, said: “We aren’t getting hotter, global warming isn’t actually happening.” A third approvingly shared an article by an explicitly climate emergency-rejecting Twitter account, Climate Realists.

Another, from 2011, contrasted the views of the longstanding climate change denier Nigel Lawson with what Trevelyan called the “ideological obsession with human-made climate change” of the then energy secretary Chris Huhne.

In a tweet collating Trevelyan’s messages, the shadow international trade secretary, Emily Thornberry, said: “At least the last Trade Secretary only hired climate change deniers … “

She was referring to a decision by Truss to appoint as a trade envoy the former Australian prime minister Tony Abbott, who has questioned policies to mitigate the climate crisis.

This month campaigners criticised the government for seemingly removing references to the temperature goals of the Paris climate agreement from a prospective trade deal with Australia negotiated by Truss.

According to Sky News in the UK, the trade deal, agreed in principle in June, was to contain references to the Paris goals of limiting global heating to 2C above pre-industrial levels, with an aspiration to a lower limit of 1.5C. Instead, the references to the temperature limits were left out, but the commitment to fulfilling the terms of the agreement was kept.

Boris Johnson, who will host the Cop26 climate summit in Glasgow in November, has committed the UK to reaching reach net zero greenhouse gas emissions by 2050.

In a statement, Trevelyan said: “This government is united in achieving our ambitious climate target goals. Having worked directly on Cop26, I am proud of what we have already done to tackle climate change and embrace a greener and cleaner future, including being the first major economy to legislate for a net zero target by 2050 and launching a bold plan for the UK’s world-leading hydrogen economy.

“As international trade secretary, climate change and protecting the environment will remain a priority as I negotiate ambitious trade deals around the world.”