Before fighting broke out in Syria, the country experienced its driest weather on record. Rainfall and snow totals were at their lowest level in Syrian history.

Now, a new study explores how rising temperatures helped influence a series of events that likely led to the country's civil war. The findings were published in the "Proceedings of the National Academies of Science".

Another report in the same publication tells how the crippling drought in the American state of California also appears linked to climate change.

FILE - In this Oct. 6, 2014 file photo, a dock sits high and dry at the end of a boat ramp yards away from the edge of Folsom Lake near Folsom, Calif. (AP Photo/Rich Pedroncelli, File)From 2007 to 2010, Syria suffered the worst drought in its recorded history.

Colin Kelley is a climate scientist. He was the lead writer of the Syrian study. He says crops failed and farm animals died across the country. He says the changing conditions forced an estimated 1.5 million people from their homes.

"And these people picked up their families and en masse migrated to the urban areas to try and survive. They weren't thinking about the future. They were thinking about the present."

Colin Kelley says many of these people fled to cities. He notes that, at the time, Syria already had as many as 1.5 million refugees from the Iraq war. Temporary housing was built in Syrian communities for the new arrivals. These communities were the same places where fighting first broke out in 2011.

Displaced Syrian families take refuge near Damascus in Feb. 23, 2015In their report, Colin Kelley and his team suggest the drought that led to the unrest was made more likely because of climate change.

They found that the weather Syria has experienced since about 1950 fits well with what models predict from increased greenhouse gases. Studies have linked rising levels of this pollution to climate change.

"When you include the long-term trend, that you are two to three times more likely to have multi-year droughts that were as severe as the most recent one."

But, he adds, it was not just the lack of rain that did it.

"We're not saying that global warming or climate change triggered or caused the uprising in Syria. What we are saying is that it basically exacerbated the drought that occurred, made it more severe -- the most severe in the observed record - and that this set about a chain of events that ultimately led to the uprising."

Another report suggests climate change has made more likely the extremely dry weather in the western United States.

One in eight Americans lives in California. The state produces 12 percent of the nation's gross domestic product – the value of all goods and services produced within the country.

Noah Diffenbaugh is a Stanford University climate scientist. He says California has wet years and dry years.

"We do know from looking at the historical record that low precipitation years have been much more likely -- greater than two times as likely -- to produce severe drought if they co-occur with warm conditions. And what we've found in California is that there's been a very clear long-term warming."

In new research, he and other researchers say that has made a drought like the current one more probable.

"That increase in probability doesn't occur without the human contribution of greenhouse gases to the atmosphere."

And in both California and Syria, the studies say the future looks to be warmer and drier still.

I'm Jonathan Evans.