AMY GOODMAN: This is Democracy Now! I’m Amy Goodman, with Juan González.

JUAN GONZÁLEZ: We turn now to look at climate change and its impact on human lives. Greece has declared three days of mourning over its worst wildfires since 2007, that have killed at least 60 people in towns near Athens, including families with children who were found clasped in a last embrace as they tried to flee the flames. Greece and other European nations have been facing record heat and an unusually dry summer. This is Prime Minister Alexis Tsipras.

PRIME MINISTER ALEXIS TSIPRAS: [translated] There are no words to describe our feelings in times like this. The country is experiencing an unspeakable tragedy. Dozens of human lives are gone, and this is unbearable for everyone, and most of all for the families who lost their loved ones.

JUAN GONZÁLEZ: This come as Japan has declared its deadly heat wave a natural disaster. At least 80 people have died from the heat in Japan, and the death toll is expected to continue to rise. In Africa, temperatures reached a staggering 124 degrees Fahrenheit earlier this month in Algeria. It was the highest recorded temperature ever in Africa.

Meanwhile, here in the United States, a staggering 41 different heat records have been broken so far this month. In California, wildfires have forced the closure of Yosemite National Park, forcing the evacuation of thousands of people.

AMY GOODMAN: Well, on Monday, a new study published in the journal Nature Climate Change, reported that when there are abnormally hot temperatures, there also tend to be higher suicide rates. The study predicts suicide rates in the United States and Mexico could actually rise with each 1-degree-Celsius increase in a month’s average temperature.

For more, we’re going to San Francisco, where we’re joined by Dr. Sanjay Basu, co-author of the new study, “Higher temperatures increase suicide rates in the United States and Mexico.” Dr. Basu is an assistant professor of medicine at Stanford University and co-author of the book The Body Economic: Why Austerity Kills.

Welcome back to Democracy Now!, Dr. Basu. Talk about this new study.

DR. SANJAY BASU: Well, thank you for having me.

The new study tries to explain a statistical phenomenon that has been observed since the early 19th century, which is: What seems to be the relationship between temperature and suicide? And, importantly, this study tries to disentangle a mere correlation from a more causal relationship, using new statistical methods. So, the study examined counties in the U.S. and Mexico from as far back as the 1960s. And after correcting for seasonality, economic changes and a wide range of other factors, we observed a direct relationship between increased average temperatures and suicides, replicating the effects observed since the 19th century of heat waves, and unusual heat waves, and excess suicides, particularly among older adults.

JUAN GONZÁLEZ: Now, could you—obviously, there might be some skeptics who would say, well, a correlation is not a cause and effect. How do you respond to those concerns?

DR. SANJAY BASU: We did a number of new statistical techniques to decipher the two. One of the most important is that we looked within the same area, over time, and looked at comparing unusual heat waves that are attributable to climate change to the typical range of heat, and then correcting for all other factors that might affect suicide rates within the area. We also controlled for a number of other variables and looked at larger data sets than ever studied before, and confirmed the findings in a wide range of other data sources. For example, we looked at over 600 million geocoded Twitter accounts where people publicly posted depressive or suicidal thoughts. We also compared that to national mortality linkages and deciphered some of the mechanisms that might explain this temperature-suicide relationship.

AMY GOODMAN: And you found a 1-degree Celsius increase in average monthly temperature correlates with increases in the monthly suicide rate in the United States and in Mexico. Talk about the differences you found in our two countries.

DR. SANJAY BASU: One of the key issues between the two countries is not only the higher average temperature in Mexico, but also some differences in the economics of the countries and in the typical work that people have in the countries. There have been prior studies that examined how people in different job sectors and at different income levels are affected by temperature increases due to climate change. In our case, we actually found remarkably consistent increases in the risk of suicide across a number of sectors, rather than simply isolated to, for example, people in the agricultural sector.

JUAN GONZÁLEZ: Yeah, I was going to ask you about that, because one would think that the impact of climate change, especially economically, would be felt even much more so on people in the countryside rather than the cities. But you didn’t see any distinct or qualitative difference between the impact for rural areas versus urban areas?

DR. SANJAY BASU: Yeah, it was rather remarkable. Over time, it appears that although in earlier years of climate change rural areas are disproportionately affected, and we do still see, for example, the relationship between a bad harvest year and increased suicides, as time has progressed and as both urban and rural populations are affected by climate change, we actually see the beginning of consistency across all groups, such that individuals across a number of employment sectors and locations appear to be almost equally affected now.

AMY GOODMAN: You also examined whether monthly temperature also correlates with patterns of depressive posts on social media containing certain keywords like “depressed,” “lonely,” “suicidal.” Talk more about that, so we’re not just talking suicide here.

JUAN GONZÁLEZ: And also, are you sure that it’s not that people get more depressed the more they use social media?

DR. SANJAY BASU: That may be a separate phenomenon. But we also looked at correcting over time for trends in social media use and how much people use these words within locations just as a temporal trend, as a routine trend over time, versus their use of these words and particular words that have, in previous studies, related to their suicide risk in unusually warm months within the same location versus normal months within the same location, and even for the same person. That helps us to try to statistically isolate the relationships of temperature, and we had some additional controls, looking at factors like employment. So there may be separate relationships, and certainly there’s multiple factors relating to mental health. We try to disentangle that portion that seems to relate in particular to increasing temperatures.

AMY GOODMAN: You also co-wrote a new study on the impact of climate change on the world’s food supply. What did you find there? And also, is there a link to farmer suicides in India?

DR. SANJAY BASU: Certainly, the issue of farmer suicides in India has been appropriately brought to light over the last few years as suicide rates seem to increase in times of economic devastation, and particularly devastation after inclement climate events. But we seem to find that there’s a second phenomenon that’s been less discussed. As carbon dioxide increases in the atmosphere, the nutritional quality of staple crops appears to decrease remarkably. The vitamin and mineral content of key crops that are the major staples for particularly low- and middle-income countries decreases in nutrient quality for important nutrients like iron and zinc, and we find, in fact, that the rates of nutrient deficiency that can lead to important diseases are expected to increase dramatically in the context of climate change.

AMY GOODMAN: Dr. Sanjay Basu, we want to thank you for being with us, assistant professor of medicine at Stanford University, co-author of the new study, “Higher temperatures increase suicide rates in the United States and Mexico,” co-author of the book The Body Economic: Why Austerity Kills.

This is Democracy Now! When we come back, how Central American activists here in this country are organizing against President Trump’s immigration policies. Stay with us.