Canada is experiencing its worst ever year for wildfires, with carbon emissions from blazes already double the previous annual record, according to the European Union’s Copernicus Atmospheric Monitoring Service.

Carbon emissions from wildfires between January and the end of July this year are already nearing 300 megatonnes of carbon dioxide, far outstripping the annual record of 138 megatonnes set in 2014.

Hot, dry weather in May and June delivered the dry soils and vegetation needed for a severe wildfire season this year, says at Copernicus.

The first serious fires broke out in May in the Canadian province of Alberta, and have since burned constantly throughout the country, hitting almost every province and forcing tens of thousands of people to evacuate from their homes. More than 120,000 square kilometres of land have been burned so far this year, according to the .

The huge scale of the fires has led to record-breaking carbon emissions, says Parrington. Copernicus uses satellite observations of fire radiative power, a measure of the heat and intensity of active fires, to estimate the emissions. “When there’s nine provinces at a time with really large-scale fires, that’s something we certainly haven’t seen in the 20 years that we have data for,” he says.

Alongside their climate impact, the fires will also be spewing out air pollutants such as particulate matter, reducing air quality. In June, smoke from fires in Quebec engulfed parts of the north-eastern US, including New York, in thick smog.

Fires are still burning across Canada, including in the Arctic circle, Copernicus announced this week, potentially fuelled by warmer temperatures in the region caused by climate change. Total emissions from the wildfires are therefore expected to keep climbing, at least for a few more weeks.

The recent deadly and record-breaking heatwave in North America would have been “virtually impossible” without climate change, according to scientists who say they are very worried about the prospect of similar events occurring around the world.

An international team has found that the heatwave, which may have killed hundreds and saw Canada’s temperature record being broken by nearly 5°C in the village of Lytton, was made at least 150 times more likely by global warming.

The temperature highs were 2°C hotter than they would have been without the human activity that has warmed Earth, say the researchers at the project. By the 2040s, they warn, such a heatwave could be another 1°C warmer.

“It’s an extraordinary event,” says at the Royal Netherlands Meteorological Institute, who contributed to the research. “A lot of people are very worried about this event. Could this also happen here in the Netherlands, France, in other places, suddenly having a 5°C jump? This is something that really needs to be researched, whether we should be prepared for this kind of jump in other parts of the world.”

Van Oldenborgh and his colleagues arrived at their findings using an approach known as extreme event attribution, whittling down 35 computer models to 21 that were best able to reproduce past weather observations in an area incorporating parts of British Columbia, Oregon and Washington. The models were then used to estimate average maximum daily temperatures in the area studied, with and without climate change.

The near-50°C temperatures recorded in Canada don’t appear in statistical models. That forced the team to artificially include the event in their models, making assumptions on the rarity of such a heatwave, which they estimated as roughly a 1 in 1000 event. The models then showed the event was 150 times more probable in a world with climate change.

Up to last year such heat in the region was impossible, says van Oldenborgh. “It’s rather surprising and shaking that our theoretical picture of how heatwaves behave was broken so [dramatically],” he says. “We are much less certain about how the climate affects heatwaves than we were two weeks ago.”

The heatwave could have just been bad luck aggravated by climate change, says the team. An alternative, more worrying, explanation is that it could be due to non-linear interactions in the climate, such as the severe drought in the south of the area studied. More research will be needed to show if such non-linearities – sometimes referred to as tipping points in Earth’s systems as the world warms – were to blame. If they were, that would show today’s climate models are too conservative, says van Oldenborgh.

The , but hasn’t yet been peer-reviewed due to the rapid nature of the work. Separate analysis, by the Copernicus Climate Change Service in Europe, shows that last month was the warmest June on record in North America.

A study of prehistoric DNA has challenged the established theory of how people first reached the Americas.

It suggests ice age people cannot have migrated to America on a land corridor between two glaciers as it was “biologically unviable”.

Conventional wisdom had it that the settlement of the Americas happened as people moved south through what is now Canada after two glaciers started to recede.

But analysis of DNA extracted from a key pinch-point suggests this was not possible as resources vital to human survival would not have been available in the ice-free corridor.

Researchers suggest it is likely that people travelled by sea instead.

An international team of researchers used ancient DNA extracted from a crucial point in the corridor to investigate how its ecosystem evolved as the glaciers began to retreat.

They created a comprehensive picture showing how and when different flora and fauna emerged and the once ice-covered landscape became a viable passageway.

No prehistoric reconstruction project like it has been attempted before.

Impassable corridor

The researchers concluded that while people may have travelled this corridor after about 12,600 years ago, it would have been impassable earlier than that, as the corridor lacked crucial resources, such as wood for fuel and tools, and game animals which were essential to the hunter-gatherer lifestyle.

If this is true, then it means the first Americans, who were present south of the ice sheets long before 12,600 years ago, must have made the journey south by another route.

The study’s authors suggest they probably migrated along the Pacific coast.

Who these people were is widely disputed.

Archaeologists agree that early inhabitants of the modern-day United States included the so-called Clovis culture, a prehistoric Native American culture taking is name from Clovis in New Mexico, where distinctive stone tool artefacts were found, and it first appears in the archaeological record more than 13,000 years ago.

The new study argues that the ice-free corridor would have been completely impassable at that time.

“The bottom line is that even though the physical corridor was open by 13,000 years ago, it was several hundred years before it was possible to use it,” said Eske Willerslev, an evolutionary geneticist and fellow of St John’s College, University of Cambridge, who led the new study.

Frozen lake

“That means that the first people entering what is now the US, Central and South America must have taken a different route,” he said. “Whether you believe these people were Clovis, or someone else, they simply could not have come through the corridor, as long claimed.”

The team gathered evidence while standing on a frozen lake surface during the winter season and applied a technique termed “shotgun sequencing”.

“Instead of looking for specific pieces of DNA from individual species, we basically sequenced everything in there, from bacteria to animals,” Willerslev said. “It’s amazing what you can get out of this. We found evidence of fish, eagles, mammals and plants.”

Crucially, it showed that before about 12,600 years ago, there were no plants or animals in the corridor.

Landscape shaped by fire

Out of the frying pan, into the fire. Caribou mothers move their calves to habitats with fewer wolves – only to put them at much greater risk of being eaten by bears instead.

Woodland caribou populations in the boreal forests of northern Canada have declined sharply in recent decades, and the government now .

Logging and oil extraction may be to blame. Human activities have fragmented the caribou’s habitat, shifting the ecological balance. Where once wolves were the main danger to young caribou, black bears now seem to be their greatest threat.

To understand this shift, at Laval University in Quebec City, Canada, and his colleagues used GPS collars to track the movements of 26 adult female caribou for up to four years. They also tracked all 44 of the calves these females had over this period, as well as 12 black bears and 9 wolves.

The data allowed the team to determine the location choices made by each caribou mother and see how that may have affected whether a calf survived to adulthood. They found that mothers that were best at avoiding wolf habitats – patches of mature forest and older tree regrowth – were more likely to lose their calves.

Wolves are the main predators of the adults and were probably also the main threat to their calves until recently. But bears are now thriving in the human-altered woodland, and the GPS records indicate that habitats that are bad for wolves are good for bears, and vice versa.

A rock and a hard place

“By being very good at avoiding wolves, they fall victim to the black bears,” says Leblond. “Mothers that are not as good at avoiding wolves in fact have better survival for their calves, because they are in regions where there’s not as many bears.” In effect, the caribou have failed to adapt to the new, bear-rich environment.

Efforts to protect caribou have focused on trying to prevent them from encountering wolves. Leblond’s findings suggest this won’t be enough.

One option currently being considered in Canada’s oil sands region would be to introduce fenced enclosures, allowing caribou mothers to begin raising their young calves without predation from bears, says at the University of Alberta in Edmonton.

The new finding also adds urgency to such efforts, underscoring that caribou mothers seemingly have no escape. “The clock is ticking here,” says at the University of Montana in Missoula. “Studies like this drive home the point that it’s worse than we thought.”