Perhaps its all because of jet envy.

That’s one explanation being given why more jets than last year are expected to carry executives, world leaders, and other luminaries this week to the Swiss Alpine town of Davos for the World Economic Forum.

It’s also a bit ironic since jets contribute to global warming and curtailing climate change is one of the leading topics on the forum’s agenda.

At least 1,500 private jets are slated to arrive in Davos. The number is up from last year’s estimated 1,300, according to the Air Charter Service, which also found that this year’s jets are larger and more expensive.

Why more and bigger jets?

“This is at least in part due to some of the long distances traveled, but also possibly due to business rivals not wanting to be seen to be outdone by one another,” Andy Christie, the private jets director at ACS said in a statement.

Over the past five years at Davos, countries with the highest numbers of private jet arrivals and departures included Germany, France, United Kingdom, United States, Russia, and the United Arab Emirates, according to ACS.

Air travel adds a significant amount of greenhouse gases into the atmosphere, with nearly 25% of emissions occurring during landing and take-off, according to a 2010 report from NASA.

The high-profile Davos confab started Monday with naturalist and broadcaster David Attenborough urging attendees to take action against global warming before it’s too late. “What we do now, and in the next few years, will profoundly affect the next few thousand years,” he implored, the Guardian reported.

The effects of global warming are well known to the World Economic Forum. Its own Global Risk Report, published earlier this year, identified climate change and environmental degradation as “the gravest threats” over the next 10 years.