Was that wild weather caused by climate change? Scientists can now say ‘yes’ with confidence

The UN’s Intergovernmental Panel on Climate Change (IPCC) has a clear message: The human-caused climate crisis is worsening extreme weather around the globe.

The world is now 1.1 degrees Celsius warmer than pre-industrial levels and is on a collision course with the critical threshold of 1.5 degrees, the report concludes, which countries in the Paris Accord agreed was the ideal limit to stave off the worse impacts.

Unless greenhouse gas emissions are slashed — and fast — the report’s authors say it’s going to get worse. With significant advances in computing power, scientists are more confident than ever in attributing extreme weather to climate change.

In June, an unprecedented heat wave in the Pacific Northwest killed hundreds of people and shattered records in Oregon, Washington and Idaho. Canada logged a new national record high when a town in British Columbia soared to 121.3 degrees Fahrenheit.

Historic heat waves are so clearly caused by human-driven emissions that researchers can now easily link them to climate change. Scientists at World Weather Attribution concluded this summer’s Northwest heat wave would have been “virtually impossible” without it.

Around the globe, human greenhouse gas emissions have already triggered more intense and more frequent hot-weather extremes, according to the report.

Some extreme weather will happen more often even at 1.5 degrees, which the world can avoid only with very low future greenhouse gas emissions. If warming exceeds that benchmark, extreme heat events will become more intense and more frequent.

Just a degree or two of atmospheric warming will translate into hotter weather for nearly the entire planet.

The climate crisis has already led to more extreme drought. More than 95 percent of the Western US is in some level of drought this summer, which has has triggered water shortages there. A major California hydroelectric power plant was forced to shut down last week when the water level in Lake Oroville dropped to a level not seen since the reservoir was filled in the 1960s.

At 1.5 degrees, droughts will become more intense and more frequent in parts of the world.

Amid unrelenting drought and record heat, wildfire seasons are now longer and result in more destructive fires. The report notes that weather conducive to wildfires can be traced to human influence.

Reports from the ground near the Dixie Fire, California’s second-largest fire in state history, suggest we are already experiencing increasingly dangerous conditions.

“We’re seeing truly frightening fire behavior, I don’t know how to overstate that,” said Chris Carlton, Plumas National Forest Supervisor. “We have a lot of veteran firefighters who have served for 20, 30 years and have never seen behavior like this, especially day after day, and the conditions we’re in. So we really are in uncharted territory around some of these extreme, large fires and the behavior we’re seeing.”

Rainfall over land has become more intense since the 1980s, and the report’s authors say human influence is the main driver.

This happens because warmer air can hold more water. Storms like Hurricane Harvey, which hit Texas in 2017, and Hurricane Lane which drenched Hawaii in 2018, not only slam coasts with storm surge and damaging winds, but also cause more intense inland deluges because of global warming.

Heavy precipitation will become more frequent and more intense with every degree of warming, the report concludes.

Monsoon rains are expected to be devastating in coming years, especially in South and Southeast Asia, East Asia and West Africa. They will also become more variable: extremely wet years with frequent floods may be interspersed with very dry years featuring drought and extreme heat.

The “weather whiplash” which will become increasingly common as climate change intensifies the global water cycle.

The report’s authors said the increase in tropical storm intensity the last 40 years can’t be explained by natural causes alone — and that humans are a contributing factor through global warming.

Scientists predict these storms will get worse as the world warms.

Hurricanes typhoons and cyclones will become more intense, top wind speeds will increase and — because of rising sea level — coastal flooding will be more extensive, the report warns.

The IPCC report is specifically focused on the past and future effects of global warming, with a large portion devoted to extreme weather — something relatable to people around the globe. The scope of the report did not include solutions, beyond noting that the best-case scenarios for reducing greenhouse gases would hold these weather changes to more manageable levels.