In early 2016, the International Energy Agency (IEA) projected that, starting that year, the world would add just 50 gigawatts of added solar energy capacity per year. And in 2017, solar's growth rate would level out and start to decline.

But as one clean energy researcher points out, the IEA may have gotten it wrong about solar's potential for growth — not just this year, but every year since 2002.

The IEA publishes annual projections about the growth rate of solar energy in its World Energy Outlook. Auke Hoekstra, a head researcher at the Technical University of Eindhoven in The Netherlands, says these forecasts are too conservative when compared to solar energy's track record.

On Twitter, he summed it up in one chart, first spotted by Mother Jones. It compares the IEA's predictions about solar energy adoption (measured in gigawatts of capacity added annually) and historic data about solar energy adoption since 2002:

Every year, the organization assumes that solar's growth rate will be linear, rather than increasing exponentially as it largely has for over a decade.

As the Guardian reported in March, the amount of new solar power installed worldwide in 2016 increased by about 50%, reaching 76 gigawatts. China and US spearheaded the surge in solar — both countries nearly doubled the amount of PV panels they added in 2015.

Globally, there is now approximately 305 gigawatts of solar power capacity, partly due to the fact that the cost to install solar panels has dropped significantly worldwide in recent years. Since 2011, it has declined 67%, according to the Solar Energy Industries Association (SEIA). If the price of solar continues to decline, adoption of the renewable energy source will likely become even more common — which doesn't match up with the IEA's flatlining projections through 2030.

"In my work with other radical innovations ... experts are simply very conservative in their own field," Hoekstra tweeted. "A conservative mindset makes it possible to reject empirical data that suggests radical change."