LONDON, Dec 18 (Reuters) - Almost half of 217 global firms cut their business travel carbon emissions by at least 50% between 2019 and 2022, analysis published on Monday found, as corporate air travel returned at a much slower pace since the pandemic than leisure flights.

Despite a global rebound, business travel has been slow to return to 2019 levels, with many corporate clients turning to video conferencing or rail trips rather than flying.

Global business travel firms say this trend could hit corporate relationships, while environmentalists argue it represents an important step in minimizing overall emissions.

Advocacy group Transport and Environment has said that a 50% reduction in business travel from pre-COVID levels is needed this decade to cap global warming at 1.5 degrees Celsius.

Major companies such as tech firm SAP, accounting firm PwC and Lloyd's Banking Group all reduced their corporate air travel emissions by more than 75% compared to 2019, the Travel Smart Emissions Tracker analysis concluded.

"The way forward is collaboration with more online meetings, more travel by train and less by plane," Denise Auclair, Travel Smart campaign manager, said in a statement.

However, the study found 21 of the companies exceeded their levels of flying compared to 2019, with L3Harris, Boston Scientific and Marriott International increasing their carbon emissions by more than 69% compared to 2019.

L3Harris, Boston Scientific and Marriott International did not respond to requests for comment.

Airlines say the corporate travel decline could harm their business and economic growth, but robust post-pandemic consumer demand for flying has tempered fears.

A joint survey by American Express Global Business Travel (Amex GBT) and the Harvard Business Review released in September said 84% of businesses believe in-person trips still bring "tangible business value".

Business trips generated as much as half of passenger revenue at U.S. airlines before the pandemic, industry group Airlines for America estimated. This helped airlines sell high-margin premium seats and fill weekday flights.

In Europe, airlines like Air France have shifted their strategies, with others trying to make up for the business drop by selling more premium trips to leisure travellers. (Reporting by Joanna Plucinska; Editing by Alexander Smith)