As Russia’s war in Ukraine led to a spike in oil prices, energy shortages in Europe, and fears that the natural gas situation will get worse, there’s been a mounting backlash against renewable energy and the idea the world is prepared to function without fossil fuels.What the world needs, according to John Doerr, chairman of venture capital firm Kleiner Perkins, is to get past the idea that it is one or the other.”Now is the time to double down on renewable, free abundant energy sources that are not controlled by petro-dictators,” Doerr told CNBC’s Andrew Ross Sorkin from the Aspen Ideas Festival on Monday. “We are funding both sides of this war now.”As a result of the current geopolitical situation, society should recognize the need for more sources of energy, and especially the need for more sources of clean energy. “It’s a false choice. We’ve got to do both,” Doerr said.He rebutted the claim that it takes too long to develop renewable energy projects to deal with the world as it is today. “In 18 months you can deploy a new solar energy at scale. You cannot build a new natural gas liquefaction plant in that same period of time,” Doerr said.He added, “The [International Energy Agency] says we don’t need to drill for any more hydrocarbons to meet the market need. We’ve got enough reserves. Develop those.”Egypt’s abundance of solar and wind will “allow generation of renewable power at a highly competitive cost – and also serve as a a key enabler for green hydrogen production.Ute Grabowsky | Photothek | Getty ImagesDoerr, an early renewable energy investor, remains undeterred in his belief that “we are in an epic transition from a fossil fuel economy to a clean energy economy. It’s the largest economic development of our lifetime, it ranks up with the internet in terms of its impact. … It’s the best investment opportunity of our lifetime, but the road will be bumpy.”In a separate interview at the Aspen Ideas Festival, Carlyle Group co-chairman and billionaire investor David Ruberstein told CNBC, “everybody wants more climate-friendly energy, of course, but it’s not easy to get there. What we’ve learned from the Russia-Ukraine war is that the world is still very heavily dependent on carbon energy, and right now, the world is scrambling to get more carbon energy.” He added, “The world is realizing you can’t go to carbon-neutral policies overnight; it will take a while.” Doerr said the the most immediate change that can be made in the energy transition is not about creating new renewable technology or producing more hydrocarbons but to cut methane emissions leaks and wasted and flared methane. He said it “is a productive hydrocarbon, but we are just tossing it into the air like it is just a free and open sewer.”He cited pledges from the large oil companies to put in place better and more effective caps and controls on their wells, as well as a project called Climate TRACE, which brings together 50 nonprofits to pool real-time data on emissions around the world, “like Google Earth, a kind of map you can track of carbon emissions and specifically focus on methane as a first and most potent gas.”Disclosure: NBCUniversal News Group is the media partner of the Aspen Ideas Festival.