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View Diary: Weekly Mulch: 'Global Weirding' VS. Climate skeptics’ slushy thinking (29 comments)

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  •  Sure it reduces the growth *rate* (0+ / 0-)

    if you reduce birth rates, but the population still keeps growing for decades either way.

    Say you have a nation of 10 million people (like Haiti).

    Birth rate close to 3% per person per year.

    If you are able to reduce the children per woman from 5 to 3, you reduce the birth rate from 3% to about 2% per person per year (younger cohorts are larger, and have had fewer children so far, so it's not quite the full 3/5 change).

    But the death rate in the country right now is less than 1% per person per year (about 0.85% in Haiti), because the older cohorts are a much smaller fraction than the younger ones, due to previous decades of population growth. So population is still growing.

    So instead of 215,000 additional people every year in this nation, you have 115,00 people per year. After 20 years we're talking about the difference between roughly 25% and 50% total population growth.

    I.e. it's still growing, but numbers are 20% or so reduced from what they would have been over that period. If that represented the whole world, the percentage improvement would be on the scale we need to tackle global warming.

    But in reality, the number of nations with fertility over 5 is down to just 27 now:

    the largest of which is Nigeria. Total population of these nations is no more than about 300 million people, or about 5% of the total world population.

    So tackling population as you suggest, means we reduce the growth rate of 5% of the world's population so that we have about 20% fewer of these people in 20 years. I.e. it's roughly a 1% effect over 20 years.

    I'm sorry, but we need 20% global effects over 20 years, 50% to 80% over 50 years. Population just doesn't cut it.

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