Republican presidential candidates have banked millions of dollars in donations from a small number of mega-rich individuals and corporations with close ties to the fossil fuel industries that stand to lose the most from the fight against climate change.

Eight out of the 17 GOP figures currently jostling for their party’s presidential nomination have between them attracted a bonanza of at least $62m so far this year from sources either directly involved in polluting industries or with close financial ties to them. Three Republican contenders stand out as recipients of this fossil fuel largesse: the Republican climate change denier-in-chief, Ted Cruz; the party establishment favorite Jeb Bush; and the former governor of Texas, Rick Perry.

The funds have come from just 17 billionaires or businesses that have pumped enormous sums – in one case $15m for a single candidate – into the support groups or Super Pacs that work alongside the official campaigns yet are free to attract unlimited contributions. The $62m forms a substantial chunk of almost $400m that has been given to presidential contenders from both main parties in 2015, raising questions about the leverage that fossil fuel interests might seek to exert over the next occupant of the White House at a critical time for the battle against climate change.

The super-wealthy donors all have connections with oil and gas operations, fracking companies, drilling firms and other activities associated with emissions of industrial carbon dioxide, the main global warming gas. Their money has gone entirely to Republican candidates, signalling a strong preference among fossil fuel billionaires for the GOP.

According to a study of donations based on filings to the Federal Election Commission carried out by Greenpeace and the Center for Media and Democracy in collaboration with the Guardian, by far the greatest beneficiary of what might be labelled fossil fuel donations has been Ted Cruz. The sitting US senator from Texas, who is among the most prominent and blatant climate change deniers in the US, has been showered with a staggering $36.5m from just four wealthy sources with links to fossil fuels interests.

Those donors include members of the Wilks family from Texas who have collectively given $15m to Cruz-supporting Super Pacs. The Wilks fortune was amassed primarily from making equipment used in fracking, a controversial technique for extracting natural gas, via a company called Frac Tech, which the family sold in 2011.

Robert Mercer, a hedge-fund manager based in Long Island, has given a whopping $11m to Cruz Super Pacs. Mercer’s fund, Renaissance Technologies, has major financial interests in big oil companies such as ExxonMobil, Chevron, Callon Petroleum and China Petroleum & Chemical Corp.

Another huge wad of cash has been pushed in Cruz’s direction by Toby Neugebauer, a private equity financier. He holds partnerships in several fossil fuel concerns including Quantum Energy Partners, an active investor in the Barnett Shale onshore natural gas field in Texas.

Cruz has made several outspoken comments disputing the overwhelming scientific consensus that man-made climate change is a serious and growing threat. In February 2014, he told CNN that data did not exist to support the “so-called scientific theory” of global warming.

In March he told the Texas Tribune that “satellite data demonstrate that there has been no significant warming whatsoever for 17 years”. Last week, at a forum organized by the energy tycoons the Koch brothers in California, Cruz made a statement described by some as “full out denial” in which he repeated his claim that “the data and facts don’t support” the phenomenon of climate change.

The Guardian invited the Cruz presidential campaign to comment on the large sums of money flowing into his coffers from fossil fuel interests, but there was no immediate response.

Such large-scale investments in the presidential race by those with links to polluting industries come at a time of mounting tension between them and US federal regulators. Last week Barack Obama announced an ambitious plan to slash carbon emissions by 2030 that could have serious ramifications for coal-powered power plants, oil extractors and natural gas producers. The Democratic frontrunner for 2016, Hillary Clinton, recently put forward her plan for a huge boost to solar power.

Connor Gibson, the Greenpeace researcher who oversaw the Greenpeace/Center for Media and Democracy study, said that fossil fuel industries were pouring money into the 2016 election cycle in unprecedented quantities. “To see so much money flowing into the war chests of viable Republican candidates so early in the race from people linked to climate change pollution is very concerning.”

Gibson said it was reasonable to ask what favors might be expected down the line as quid pro quo. “Will these candidates be expected to roll back federal oversight and regulation of fracking and methane leaks? Will they be more likely to allow drilling in the Arctic at a time when scientists are warning that fossil fuels must be kept in the ground?”

But David Keating, president of the Center for Competitive Politics, which calls for all restrictions on political donations to be lifted, said that “way too much was read into numbers like these. Most people at this stage of the election cycle are giving because they believe in what the candidate stands for and their policies, rather than because they are trying to influence those policies.”

The American Petroleum Institute, a national trade association for the oil and natural gas industry, said it was only to be expected that money was being donated to presidential candidates by people in all walks of life, not just the energy sector. “Candidates running for president receive campaign contributions from all industries, including the wealthy environmental community, as part of our constitutional right. For API, our candidate is energy and its importance to jobs, revenue to the government and our national security,” said Sabrina Fang, an institute spokeswoman.

The second-largest recipient of major donations from sources linked to polluting industries is Jeb Bush, the former governor of Florida who has positioned himself as the leading moderate in the GOP field. Super Pacs supporting his bid for the White House have banked a total of $13.3m from nine separate donors.

Those donors include Rooney Holdings, which gave $2m to Bush. The company’s chief executive, Francis Rooney, a former United States ambassador to the Vatican, serves on the board of the independent oil and gas exploration firm Laredo Petroleum as well as on the board of Helmerich & Payne Inc, one of the world’s main offshore platform drilling contractors.

Other Bush backers are Richard Kinder, co-founder of Kinder Morgan, an energy infrastructure company that owns 84,000 miles of pipeline; the oil magnate Trevor Rees-Jones; and Dallas oil billionaire Ray Hunt.

Bush has been more measured in his comments on global warming than Cruz, and has publicly stated that the climate is changing. But he has injected a note of doubt into the debate around the science of global warming and what should be done about it.

On his very first day of official campaigning in June, he criticised Pope Francis for his outspoken call for drastic change to avert the “unprecedented destruction of the ecosystem”, telling the pope to keep out of global affairs. In May, Bush called the science on climate change “convoluted”, lambasting the vast majority of scientists who say it is now beyond doubt as “really arrogant”.

He added: “I don’t think the science is clear what percentage is man-made and what percentage is natural.”

The third big recipient of cash from donors linked to polluting industries is the former governor of Texas, Rick Perry. His Super Pac, Opportunity and Freedom, has been given $6m by Kelcy Warren, owner of the Texas oil and natural gas pipeline company Energy Transfer Partners. In addition to vast sums, Warren is also donating his time – he is working for the Perry campaign as its finance chairman.

Perry has frequently denied that climate change is a scientific given. Last June, for instance, he said: “I don’t believe that we have the settled science by any sense of the imagination.”

He added: “Calling CO2 a pollutant is doing a disservice the country, and, I believe, a disservice to the world.”

Five other Republican presidential candidates have received smaller amounts from those linked to fossil fuels: Carly Fiorina ($.2m), Lindsey Graham ($1m), Bobby Jindal ($1.2m), Donald Trump ($1.8m) and Scott Walker ($1.8m).

True to form, Trump stands in a class all his own. He is not only one of the GOP recipients of largesse from a donor with links to polluting industries – he also happens to be that donor.

He contributed $1.8m to support his own campaign. As the Greenpeace/Center for Media and Democracy study pointed out, Trump has substantial shareholdings in several non-renewable energy companies including ConocoPhillips, ExxonMobil and Occidental Petroleum.

According to financial disclosure records, he also has $250,000 worth of stock in TransCanada Pipelines Ltd. In 2011, he was reported as saying that it is “an outrage our president isn’t approving the Keystone pipeline”, the oil pipeline that runs from Canada to the US that has become a focal point of environmental agitation over combating climate change.