Because there are a ton of new manufacturing facilities for wind and solar under construction, so you expect to see a sudden jump. The IEA then assumes no further policy changes to cause adoption rates to increase at the same rate as that jump.
I would say it is, because the IEA cannot take the responsibility for it, if it really does grow exponentially.
Like, what if that exponential grow stops for any reason. People are gonna blame the IEA for overestimating our abilities, potentially causing negative side-effects.
So, the IEA tries to "play it safe" with their prognosis.
The two most populated countries in the world are investing heavily into renewables? Sounds good to me.
China and India are dedicated to improving the standard of living of their citizens. Those citizens need energy. The idea that China and India would invest heavily in non-renewable fossil fuels to meet that need - or worse, nuclear - was yet another potential climate nightmare. The fact that they're emphasizing renewable energy sources is one small bright note in the dark clouds ahead of us.
Germany also built a lot of solar energy infrastructure last year, as far as I know. We have a tracker on the news website zeit.de. But wind energy is still behind sadly.
Hydropower is one of the most widely available and effective sources of non-fossil fuelled electricity generation. If we're going to have a chance to stop climate change we need to use it to its fullest..
This doesn't have a section for energy storage, which is exploding right now as well. That's a big part of the story that makes this good news even better.