From space, the Earth looked very different from what modern humans would expect today. For one thing, the Panama isthmus did not connect North and South America, allowing direct low-latitude circulation between the Atlantic and Pacific Oceans. There was no Drake Passage separating South America from Antarctica and the Arctic was also more restricted.

It came from space. The object, impacting on or near the coast of what is now called New Jersey. There was an abrupt release of carbon into the atmosphere causing global climate warming at an accelerated rate. It took decades or centuries, not thousands or tens of thousands of years for the planetary temperature to rise 5 to 9 degrees Centigrade or about 9 to 16 degrees Fahrenheit.

Numerous single-celled ocean bottom organisms became extinct while other surface species moved to the poles in order to survive.

Overall, the climate became wetter, Arctic freshwater concentrations increased, and although there was a general lack of global ice, sea levels still rose due to thermal expansion.

“Dr. Barnes, you’re not saying that this impact over 55 million years ago caused modern climate change. That’s not what you explained to me before.”

“Of course not, Colonel. However it is necessary to…”

“Wait a second.” Aiyana Zheutlin interrupted Project Retrograde’s top scientist before he could finish. “I thought the Paleocene–Eocene Thermal Maximum was caused by vulcanism over thousands of years of time.”

“Ms. Zheutlin, I’ve researched this thoroughly, and although conventional opinion would agree with you, I have two factors on my side. The first is that after your return from Atlantis, the time map shifted again, indicating the occurrence of an additional time storm and one of the events is centered directly on the genesis of the PETM event. The second is that we’ve been running weeks of time gate excursions, first observing the actual impact, and then sampling the climate and general environment over regular periods of time, from ten to a hundred years, using both atmospheric drones and orbital satellites.”

“Satellites? That’s outrageous. Who authorized that sort of historical incursion?”

“Why Colonel Kelgarries of course, Dr. Ashe.” Dr. Barnes waved his hand toward the military commander of the project.

Aiyana bristled at Barnes referring to her as “Ms.” and to Ashe as “Dr.” when he full well knew she possessed two doctorates.

“What’s your point, John?”

“Gordon, the point isn’t about the PETM event being the direct cause of modern global warming. Obviously, it isn’t. But the time storm caused by the launching of…of whatever from Atlantis nearly 4,000 years ago seemed to have changed the cause of that event from volcanic to extraterrestrial. They’re both still natural events, but with startlingly different implications.”

“Climate change happening suddenly, in decades or a century vs. millennium.”

“Exactly, Aiyana.”

“If I may continue.” Barnes was a smug son-of-a-bitch, but he was also brilliant. “I’m drawing our attention to the PETM event as a sort of model or example. I believe a similar event triggered our own current climate change, a sudden and dramatic impact occurring approximately one hundred years ago.”

“Oh shit.”

“Oh shit indeed, Dr. Ashe. I believe you know what I’m talking about. If not, it is clearly identified here on the time map.” Barnes again waved with flourish at the display on the wall behind him.

“I’ve read about it, Gordon, but…”

“Quite, Dr. Zheutlin. In 1908, June 30th to be precise, an explosion tore through the air above a remote forest in Siberia near the Podkamennaya Tunguska river. The fireball has been estimated to have been between 50 to 100 meters wide, depleting 2,000 square kilometers of the Taiga forest and laying absolutely flat 80 million trees.”

“The Tungusta Event“.

“Yes, Dr. Ashe, the Tungusta Event, and if I am correct, it was this explosion that most likely caused or at least gave a ‘jump start’ to modern climate change, just as the PETM event did 55 million years ago.”

“But that’s incredible, Dr. Barnes. If our mission is to reverse or prevent climate change, and it was caused by a giant meteor or comet from space, how the hell can we ever do anything about it?”

“That’s just it, Dr. Zheutlin. What if the Tunguska Event was not natural but rather caused by artificial means?”

“Forerunners? Only a century in our past?”

“Orange Forerunners, Dr. Ashe, and I specifically refer to the individual Ross Murdock encountered at Atlantis. I believe that single individual is responsible for potentially causing human extinction within the next fifty years, and it is the responsibility of your team to stop the alien by whatever means possible.”

This is a new book and direct sequel to the events that took place when the “defiant agents” escaped a doomed Atlantis and returned to the present. Careful study of data gathered by team member Lynn Huỳnh has indicated that an Orange Forerunner launched a controversial power source from the island, triggering not only the island chain’s destruction, but a devastating time storm. The events discussed in this brief prologue are just some of the results.

I’ve peppered the prologue with links to my source material, but for more reading, see Comet Collision Could Have Caused Rapid Carbon Rise and A comet impact may have triggered Earth’s ancient warming period. There’s ample evidence (at least for science fiction) to suggest that a similar event less than 110 years ago may have had the same general effect on our world.

This isn’t to say that the human industrial age hasn’t contributed, however, the Tunguska Event may have given it a great big push.

Stay tuned for the next installment for more action in my continuing homage to the works of Andre Norton (Alice Mary Norton).

The next chapter is Threshold.