If humans produced 29 billion tonnes of carbon dioxide in 2016 and this is set to grow by around 40% by 2035, then the total amount of carbon dioxide that will be produced by humans in 2035 is 29 billion + (29 billion * 40%) = 29 billion + 11.6 billion = 40.6 billion tonnes. In standard form, this is 4.06 * 10^10 tonnes.