Of course it's not all sunshine and rainbows. Meeting the $5.1 trillion global renewable energy investment from 2011 to 2020 will require a five-fold increase from current investment levels. And of course there is the political challenge involved in implementing the necessary policies to allow this renewable energy investment increase to happen. For example, putting a price on carbon emissions, which will more accurately reflect the true cost of fossil fuel combustion in their market price, and make renewable energy more financially competetive. However, even though doing so would be economically beneficial, as the SRREN notes, there is a great deal of political resistance to implementing a carbon price in many countries.
To sum up, in this report the IPCC finds that we can give ourselves a chance to keep global warming below the 'danger limit' with an investment of less than 1% of global GDP in renewable energy. This will also help us de-couple economic development from GHG emissions, and in fact will benefit the economy by avoiding the harm to public health and the climate associated with burning fossil fuels. However, accomplishing this major transition from fossil fuels to renewable energy will be very challenging, particularly from a political standpoint in terms of implementing the necessary policies.