VATICAN CITY (TheBlaze/AP) -- Dozens of environmentally friendly mayors from around the world will be signing a Vatican declaration Tuesday urging their national leaders to approve a "bold climate agreement" that keeps global warming at a safe limit for humanity, the Associated Press learned.
Some 60 mayors are attending a two-day climate conference at the Vatican featuring an audience with Pope Francis, whose recent environment encyclical is aimed at keeping up the pressure on world leaders ahead of Paris climate negotiations in December.
In one of the opening speeches, California Gov. Jerry Brown denounced global warming deniers who he said are "bamboozling" the public and politicians with false information to persuade them that the world isn't getting warmer.
Brown, a former Jesuit seminarian, urged the mayors to not be complacent in opposing climate deniers. California has enacted the toughest greenhouse gas emissions standards in North America.
"We have a very powerful opposition that, at least in my country, spends billions on trying to keep from office people such as yourselves and elect troglodytes and other deniers of the obvious science," he said to applause.
The final declaration, a copy of which was seen by the AP, states that "human-induced climate change is a scientific reality and its effective control is a moral imperative for humanity."
The document calls for financial incentives to transition to low-carbon and renewable energy and to shift public financing away from the military to "urgent investments" in sustainable development, with wealthy countries helping poorer ones.
And it says political leaders have a "special responsibility" at the Paris talks to approve a "bold climate agreement that confines global warming to a limit safe for humanity, while protecting the poor and the vulnerable from ongoing climate change that gravely endangers their lives."
Other mayors attending hail from Boston; Boulder, Colorado; New York City; Oslo, Norway; San Francisco and Vancouver. Many belong to the new Carbon Neutral Cities Alliance, whose members have committed to reducing greenhouse gas emissions by at least 80 percent by 2050 or sooner.
Other mayors hail from the developing world, including Libreville, Gabon; Siquirres, Costa Rica; and Kochi, India.
Experts have long said that cities are key to reducing global warming since urban areas account for nearly three-quarters of human emissions.
In his sweeping manifesto last month, Francis blamed global warming on an unfair, fossil-fuel-based industrial economic model that harms the poor the most. Many conservatives have rejected or dismissed the encyclical as flawed and irresponsible.
In addition to the climate declaration, mayors will be asked to sign a statement against human trafficking.
In the scientific realm of climate change, a study published this week clarified that the "slow down" in the rate of global warming doesn't suggest an end to global climate change. Instead, the study from researchers at the University of Edinburgh says the slow-down is natural and that an increase in global temperatures will continue in the long term.
"Human activity is causing the word to warm, and natural variability can cause this trend to slow down or speed up," Dr. Andrew Schurer of the University of Edinburgh's School of GeoSciences, who led the research, said in a statement. "Our study backs scientific understanding that climate change can experience periods of hiatus, but the overall trend is towards a warmer planet."
Based on calculations by the National Oceanic and Atmospheric Administration, 2015 will likely be the warmest year on record with June and the first six months of this year already beating temperature records.
NOAA calculated that the world's average temperature in June hit 61.48 degrees Fahrenheit, breaking the old record set last year by 0.22 degrees. Usually temperature records are broken by one or two one-hundredths of a degree, not nearly a quarter of a degree, NOAA climate scientist Jessica Blunden told the AP.
The old record for the first half of the year was set in 2010, the last time there was an El Nino event — a warming of the central Pacific Ocean that changes weather worldwide. But in 2010, the El Nino petered out. This year, forecasters are predicting this El Nino will get stronger, not weaker.
Watch this report from the Weather Channel on the record:
The Associated Press contributed to this report.