It is very amusing that some are still saying climate change is not happening. The Senate in the US has just passed a resolution created by Republicans who in the past have been staunch deniers that climate change is happening. But, the Republicans will not admit to humans having any impact on the climate. In other words, they recognized that the carpet was being pulled from under them with what has been developing climate wise over decades.

2015 is not in a prime position for climate change with warm Ocean currents travelling into the Arctic Ocean from the Pacific and North Atlantic Oceans plus the soot as shown in the photos referenced below.

http://www.slate.com/blogs/future_tense/2014/09/16/jason_box_s_research_into_greenland_s_dark_snow_raises_more_concerns_about.html

Guy's article is a timely reminder that climate refugees need to be considered. The Marshall Islands had been overwhelmed by seas twice last year; salt water has an impact on soil

For me there are two key points in this article:
a) population growth and resources are out of balance
b) we have to fix the problem in situ, that means locally. Shifting people around is futile and does not solve the problem. I would add that it makes the problem worse as it leads to loss of social cohesion followed by internal conflict, parallel societies, civil wars.
Education and re-directing foreign aid, perhaps a carrot-and-stick approach, are the suggested means to achieve a better outcome.
But it does not end there. Cultural and religious barriers create walls that need to be dismantled, and that is the really hard part.

@ Banjo, most focus upon the headline figures which can appear alarming, but the real data shows trends e.g. crashing fertility rates, and static numbers of youth internationally (think 2 billion now, will be about 2 billion in a 100 hundred years).

Prof. Hans Rosling (statistician, doctor and development expert) explains well as featured in The Guardian http://www.theguardian.com/global-development/2013/may/17/hans-rosling-data-population-fertility

and several demographers have looked at trends with Deutsche Bank predicting that peak population will not be reached..... the only significant fertility being in sub Saharan Africa.

However, those reports that predict or project increased headline population don't seem to feature that salient points i.e. fertility rates have dropped below replacement level, and that is it prosperity i.e. education and health leading to people living longer, therefore it is old people impacting the data creating a spike..... which will subside over time due to lower fertility.

Ehrlich's claim to fame was highlighting fertility, less developed countries, non-Europeans and the 'population bomb' coming to outnumber the western world, coincidentally something neo cons (+ media) fret about, and use to alarm their constituencies....

In fact Robert Reich describes it correctly, as Ehrlich is not a demographer. We are not dealing with high fertility rates or inputs, but a 'baby boomer bomb' due to longevity from prosperity.... but from Malthus through governments and advocates today, they same intent on blaming poor brown people for the western world's profligacy = maintaining the status quo.

As Rosling says, it's not how many many (i.e. headline figure), but how we manage our resources in an equitable way to deal with ageing populations, and limited working age populations.

This graphic of Australia's age distribution allows comparison from 1900 to the present and on through projections to 2100, with the population divided into 5 year intervals.

http://www.abc.net.au/news/2011-08-09/interactive-infographics-census-2011-australia-transformed/2829132

If you look at 2015, you will see that only 15.3% of the population is over 65, and no elderly interval is as large as any of the younger intervals. Even if you look at the projection for 2030 (for what it is worth), only 19.8% will be over 65. Globally, the problem of people living longer is trivial compared to the problem of demographic momentum. In any case, the very low life expectancy figures of, say, 200 years ago were mostly due to very high mortality before the age of 5, as well as lots of deaths in childbirth.

Historically, the First World is responsible for most greenhouse gas emissions that are currently in the atmosphere, but the biggest emitter today us China, and it is still the biggest, even if you exclude production for export.

http://www.wri.org/blog/2014/11/6-graphs-explain-world%E2%80%99s-top-10-emitters

This is not because the average Chinese person is living it up.

Blaming poor brown people for everything that is wrong in the world is stupid, but so is claiming that poor brown people can do no wrong, or if they do, it is really our fault.

The bottom two billion in the world are relatively blameless when it comes to greenhouse gas emissions, as shown in this video by Hans Rosling

http://www.theguardian.com/global-development/video/2013/may/17/population-climate-change-hans-rosling-video

Nevertheless, they are responsible for a lot of the deforestation and extinctions, as well as the land degradation. Making them more prosperous would help to bring down fertility rates in the countries where they remain high, but it would also mean more pressure on our life support systems, which are best understood by natural scientists, not demographers. Nor would it do anything for demographic momentum in the countries where fertility rates have already dropped.

Last updated in 2012 at five minutes to midnight, the clock has moved forward two minutes as the Bulletin of Atomic Scientists grows further concerned about the emissions trajectory.

Divergence,
the interactive graphs are great!

Just a couple of points along the lines I argue that not enough consideration is given to the economic forces that underwrite past, present and future demographics.

First, when you say: "Nevertheless, they [the poorest two billion] are responsible for a lot of the deforestation and extinctions, as well as the land degradation", you don't acknowledge that these populations are slave to global capitalism, and that deforestation etc. is mostly the consequence of first and second world demand for resources and cheap commodities/labour.

Second and more important, looking at the hans-Rosling video, he paints far too rosy a picture of a kind of equilibrium he foresees in 2100, whereby the world is 'united' in conspicuous prosperity and population has stabalised around 10 billion, his only requirment being that we all produce less greenhouse emissions at that time.
This is naive in the extreme in that cuts in emissions can only be made finally via cuts in consumption, which can only be modified/attenuated to a limited degree, and not so as to be both 'prosperous' (in any way we currently define the term) and 'renewable'.
No account of the strife that must occur during this century is mooted, but it also fails to account for how we got there, or how this utopia will be supported economically when the growth of new markets--along with the satiety of old ones--will be exhausted.
hans-Rosling's idea of monolithic prosperity also fails to breakdown the actual disparities which obtain within; these are vast and the picture Thomas Piketty has recently painted shows "patrimonial capitalism," and all its social implications, again in the ascendency.
Even putting aside the drastic inequities which mark "prosperity" generally, even if we accept this as a necessary state of affairs, unless there's a paradigm shift in what that means, it can't be sustained in a human world (it will be practically a human monoculture) that has reached its natural limits.