Gavin Schmidt, director of NASA's Goddard Institute for Space Studies, during a visit this month to attend a conference at the University of NSW. Credit:Dean Sewell

The eruption of pine bark beetles that has devastated millions of hectares of forests in North America is an example of the surprises yet to come as the planet warms, says Gavin Schmidt, head of NASA's Goddard Institute for Space Studies.

The tiny beetles, which have infested forests from Colorado to Alaska, develop a type of anti-freeze as winter arrives. With fewer cold snaps before the insects are "cold hardened", more of them are making it through to spring.

“We just don’t understand ecosystems to the extent we understand the physical climate systems," Dr Schmidt told Fairfax Media during a visit to Sydney. “We will see over the next few decades more and more thresholds being crossed.”

However, that's not to say the physical climate is fully understood either.