The operational emissions coming from Irish firms taking part in a global environmental disclosure scheme fell by 36% last year.
The annual report of non-profit organisation CDP also shows that eight new Irish companies, including Paddy Power owner Flutter, Woodies owner Grafton and aircraft leasing company AerCap, joined the initiative, an increase of 17%.
However, 21 other large Irish businesses failed to respond to requests to report their emissions, something that CDP Ireland Network claims will put them at a competitive disadvantage.
"This is a minimum first step companies should take to demonstrate to their investors, their customers, and their staff that they are taking their responsibilities seriously," said Eoin Fahy, chairman of the CDP Ireland Network.
"An increasing number of companies are putting in place scientifically verified Net Zero targets, with specific plans in place for how these will be achieved."
"Vague aspirations to go green are no longer good enough; it must be backed up by concrete proposals."
The report shows that average Scope 1 and Scope 2 emissions per responding firm came to a total of 32,577 tonnes of CO2 equivalent in 2021.
This compares to 50,483 a year earlier, a decline of more than a third.
However, some of the decrease is the result of a Covid-19 pandemic caused slowdown in activity, with the smaller size of some of the new firms reporting also dragging the average down.
79% of Irish respondents received a B- grade or higher compared to 69% across Europe and 66% globally.
The top ten Irish companies for reducing emissions included Accenture, AIB, CRH, ESB and Glenveagh Properties.
CDP Ireland said 19 companies that report to it have received approval under the Science Based Targets Initiative, which sees companies set targets required to keep global temperature increase well below 2 degrees, while a further 25 have committed to setting them.
But CDP Ireland claims much more has to be done, as just 1% of firms globally who submit their emissions data have given their investors a credible plan for transitioning to low-carbon use.
The organisation says companies need to speed up their decarbonisation plans, particularly around Scope 3 value chain emissions.
"With more transparency comes bolder ambition, as companies recognize the benefits of acting early to mitigate the risks of business as usual and take a leadership position," said Maxfield Weiss, Executive Director of CDP Europe.
