The current ice age
The planet earth is currently in the middle of an ice age.
At regular intervals polar ice caps expand, causing widespread glaciation and
causing widespread devastation to the planet's ecosystems.
This graph illustrates the temperature during the most recent glaciation cycles:
Recent global temperatures (from ice core data here)
One thing is pretty obvious from this data - we are very near the end
of the current interglacial period - and a new glacial cycle is imminent -
indeed, probably overdue.
Reglaciation would represent an apocalypse for life in the northern hemisphere
- humans should be doing everything they possibly can to prevent this from
The current ice age has lasted 30 million years so far. Glaciation currently
happens every 100,000 years on a very regular cycle.
This graph illustrates the glaciation cycles:
Ten in the last million years - and they happen with considerable regularly.
The cause of glacial cycles
Until relatively recently the preferred explanation for these cycles was [Milankovitch cycles
]. Milankovitch cycles are periodic variations the Earth's orbit, caused by
factors such as precession of the elliptical orbit of the Earth, and changes
of its axial tilt. However, this theory suffers from [many
problems]. More recently some other theories invoking other astronomical
effects have been developed.
One theory is described in the document:
Sun's fickle heart may leave us cold.
The associated article is here:
diffusion waves as a driver of terrestrial climate change [PDF].
The other theory involves changes to orbital inclination - an effect
not understood in Milankovitch's day. This theory was pioneered by Richard
Muller and Gordon MacDonald. The theory is summarised on Richard Muller's web
Because of the problems with the Milankovitch cycle theory, these other theories
may be preferable.
Interglacial cycles are regular - but patyly because of the considerable
uncertainty about the causes of interglacial cycles and the possible
effect of human action on the climate, nobody really knows
exactly when the current one is likely to come to an end.
The possibility of reglaciation
Whatever the causes of the temperature cycles, we are currently in an
interglacial period. However we are still in an ice age. If
temperatues begin to drop again, large ice sheets will form. These will
increase the Earth's reflectivity and reduce the absorption of solar radiation
- creating positive feedback that leads to runaway cooling - and a catastrophic
drop in global temperature.
During glacial periods our planet is cold, dry, and inhospitable. Winters are
longer and more severe. Few forests can survive but there are plenty of
glaciers and deserts. Glaciers scrape up and pulverize vast stretches of land
scraping off vegetation and topsoil and completely destroying entire
ecosystems. In their wake they leave altered river courses, flattened
landscapes, and piles of broken rock.
Overall, an ice age is an abnormal and relatively-rare state of affairs.
They are usually temporary and fleeting sicknesses for the planet. Details are
Ending the ice age - if that is a practical possibility - would return the planet to its
Ending the ice age
It should be obvious that ending the current ice age - and its regular cycles
of glaciation - should be a matter of high priority. The current cycle of
devastating glaciation must not be permitted to continue - since the cycles
destroy a lot of the life on earth - and turn much of the planet into a frozen
If humans can successfully heat up the planet - and perhaps totally
melt the ice caps - the next cycle of glaciation might conceivably be avoided
- and we might successfully end the current ice age.
Here is Freeman Dyson on the problem:
In each hundred-thousand year period, there is an ice-age that lasts about
ninety thousand years and a warm interglacial period that lasts about ten
thousand years. We are at present in a warm period that began twelve thousand
years ago, so the onset of the next ice-age is overdue. If human activities
were not disturbing the climate, a new ice-age might already have begun.
Ice age causes
The geological record appears to show that ice ages start when the continents
are in positions which block or reduce the flow of warm water from the equator
to the poles and thus allow ice sheets to form. If incoming solar radiation
diminishes, ice sheets form. These increase the Earth's reflectivity and thus
reduce the absorption of solar radiation. This creates positive feedback that
leads to runaway cooling.
Currently we have the continent of Antarctica sitting on top of one pole, and
the the Arctic Ocean is almost land-locked - so circulation around both poles
of the planet is restricted, preventing ice from encountering very much warmer
This situation looks unlikely to change any time soon - and it is difficult to
imagine us being able to do much to change it. The continents are still in a
configuration where the earth is prone to glaciation.
While oceanic circulation is challenging for humans to assist, other effects
may be easier to control:
To some extent the planet's temperature depends on its albedo. Making the
planet darker should successfully raise its temperature.
Currently the easiest way to darken an area of land is to plant trees on it -
Vegetation absorbs much light from the sun, and re-radiate it as heat.
Forests are more competent at this job than other kinds of vegetation.
Trees heat up the planet by making it darker, so that it absorbs more heat, and
by transpiration, where water vapour is created by leaves for cooling purposes
during photosynthesis. They temporarily take some carbon out of
circulation - but most of it is returned to the atmosphere when their
leaves fall in autumn and rot - and when the tree trunk rots it dies. This
recycling of organic matter is quite efficient - and typically only a small
fraction of the carbon from dead plants winds up buried in accumulating
sediments and is eventually subducted.
One place to try developing forests is deserts. The main problem in
those regions is lack of water - and water could be provided by irrigation
projects - dams, canals and pipes.
Another place is northern wastelands. Trees have the biggest effect
on albedo if they turn snow-covered ground into evergreen forests - that
shrug off snow and remain dark.
Albedo effects trump greenhouse effects, in a sense: reflected radiation is
more likely to carry energy away from the planet than radiation that has been
absorbed and re-emitted in all directions and at low wavelengths - and in terms
of molecular vibrations - as heat.
Once energy has turned from radiation into jiggling molecules, its
chance to escape into space has been lost - and that's what happens
when radiation hits plant leaves.
Reflections from - e.g. water droplets - give high frequency,
penetrating radiation a second chance to be turned into low
frequency non-penetrating infra red radiation and heat by leaves -
but the importance of this effect is reduced if the radiation is
likely to have hit leaves the first time it hit the surface.
In the more distant future it seems likely that we will develop floating
fertiliser delivery systems - and surface-living ocean organisms will become
possible. These may be capable of rolling a green carpet over large areas of
seawater, if we are prepared to fertilise them. In this way, it may be possible
to convert areas of ocean into a farmable surface. This would make the planet
absorb more sunlight.
In order to increase the scale of the plant life on the planet, we will
also need more essential minerals and nutrients. Phosphorus is an important
limiting nutrient for many plants. This can be obtained by mining.
More carbon, iron, copper, zinc and magnesium may also be needed - all
can be obtained by mining.
Clouds - particularly high clouds - make the planet reflect sunlight
back into space. Clouds are a natural planetary thermostat that hinders
attempts to increase the planet's temperature: the hotter it gets, the more high
clouds form, and the more radiation is sent back into space.
This thermostat doesn't work so well at low temperatures. The cooler it
gets, the fewer clouds form, and the less rain there is. If this causes
enough plants to die, the planetary albedo suffers, and the earth is
then in danger of turning into an icy ball.
Controlling cloud seeding using micro-organisms or small particles
seems like a desirable skill - if we can master it.
Another influence on the global temperature is the composition of atmospheric
gasses. These have the power to influence what frequencies of light are
re-radiated into space, by bouncing them back down to the earth from the
atmosphere, in what is known as the greenhouse effect.
By exploiting this effect, we may be able to turn the planet into something
more like a greenhouse - warmer and more hospitable to both plant and
The greenhouse effect results in something analogous to wrapping a warm blanket
around the planet. Trapped heat results in the poles heating more than the
equator - so that heat is applied to the planet in the areas that are least
hospitable to life - and so need it the most.
The insulating effect means that temperature variations over time
will become less extreme - meaning that living and non-living systems will
have to withstand reduced stress from thermal variations.
A stabilisation of temperatures between the poles and the equator should also
lead to a reduced global temperature gradient, and reduced wind levels.
On the other hand there will probably be more evaporation, precipitation - and
thus more thunder storms.
More precipitation is basically good. It will help irrigate the world and
allow for plant growth - and will help to reduce desertification and forest
fires. However, not everyone will enjoy a more stormy planet.
Obviously a warmer planet is highly desirable for other reasons -
besides averting the global catastrophe that re-glaciation represents.
Much of the continental land mass is concentrated around the poles.
Russia, Europe, Canada, Greenland and Antarctica would all have their climate
vastly improved if they were warmer. These regions contain large areas
which represent potential environments for living systems but which are
currently largely uninhabited, due to adverse temperature
Run global warming scenarios backwards in time and you get a global
catastrophe - where large, previously habitable areas of the planet
are reduced to icy wastelands.
Here are some of the areas that will benefit from global warming:
Most of the human population of the planet exists around the equatorial belt.
Russia and Canada are largely uninhabited because their temperature is too
low. Also, Saharan Africa is too dry - and would benefit from additional
The equatorial region of the planet is mostly water. Oceans
are mostly empty, inhospitable wastelands as far as living system
go: nutrients all sink to the bottom - where there is no light - and
on the surface there's nothing to eat.
This distribution of land - where the land is concentrated around the poles -
is actually what causes ice ages in the first place. Polar land masses
prevent warm water from equatorial regions circulating around the frozen areas,
and allow ice formed over the winter to persist over the summer - and thus
Cold kills. Here is Freeman Dyson on the topic:
Thereís a lot made out of the people who died in heat waves. And there is no
doubt that we have heat waves and people die. What they donít say is actually
five times as many people die of cold in winters as die of heat in summer. And
it is also true that more of the warming happens in winter than in summer. So,
if anything, itís heavily favourable as far as that goes. It certainly saves
more lives in winter than it costs in summer.
Freeman Dyson is right about this. Heating the planet up a bit seems likely to
save many lives.
Ice age climates are inherently unstable. That is because they are
characterised by positive feedback - and are prone to flipping between
extreme states. The cause of this positive feedback is the fact that
ice and snow are white - and reflect incoming radiation back into space.
This cools the planet, which in turn causes more ice and snow to form.
When the planet is not locked in an ice age, its climate is more
stable. That is because such eras are characterised by negative feedback. The
cause of this negative feedback is the fact that any increases in temperature
cause water to evaporate, which forms white clouds - which reflect incoming
radiation back into space, which cools the planet down again.
Greening the deserts
Saharan Africa is much too dry. Deserts are largely an ice-age phenomenon - for example, the Sahara desert formed during the current ice age. The main problem is lack of precipitation. A bigger greenhouse effect will heal the planet's deserts, and transform them into vibrant living ecosystems.
This is already underway. The phenomenon is known as Global greening.
The warming process will inevitably be slow. It is estimated that it will take
about a thousand years for the Greenland ice sheet to melt. Antarctic will
probably take much longer. It is about -37 degrees C down at the pole,
and the ice is an average of 2 kilometres thick.
Because of the inevitable slow rate of progress, there will be plenty
of time for living organisms to adapt to the changes.
For some reason, certain factions seem to have got hold of the idea that
warming the planet up is bad.
They point to flooding, coral bleaching, forest fires and other problems
as indications that change is undesirable.
Warming the planet might have some side effects, it is true - but
at least it helps avoid the devastating global catastrophe that
re-glaciation would represent.
It seems to me that many of these folk are luddites - who see the issue
as a good excuse to place limits on industrialisation and growth.
You might think environmental groups would be in favour of
improving the habitability of the planet by getting rid of the parts of it
that are uninhabitable frozen wastelands. You might think that they
might regard CO2 as plant food - and would embrace plans
to pump it into the atmosphere. However, they seem to be more interested in
polar bears, bush fires and floods.
This attitude raises the question of whether humanity is too stupid to see
the problem - and will fail to take the required action to prevent
I am optimistic about our chances. We probably have enough time to
execute this plan, and - despite the protests of objectors - progress
is now clearly being made.
There is an evolutionary pressure to occupy vacant ecosystems. Now that life
has become more adept at mastering technology, it is in a good postition to
succeed. It seems likely that living systems will use their expertise to expand
out of the equatorial band and colonise the rest of the planet, increasing
the planetary albedo in the process, and tipping the planet away from its
current frozen state.
The likely outcome of all this is that [ocean reclamation] will
take place - and most of the planet's surface will become covered with
solar energy collectors - resulting in a significantly warmer planet,
with fewer icy wastelands.
Success will require increased efforts in these areas:
- Mining - to supply the required nutrients for all the new living organisms;
- Irrigation - and other resource distribution schemes;
Accelerate Global Warming
So far, progress has been rather slow.
Slow progress leaves the planet close to the edge - and means that the
climate is vulnerable to developing into another glacial era.
For example, it is widely theorised that human efforts are already
responsible for preventing another glacial period from starting. If
humans are all that's keeping the planet from freezing, then catastrophic
events - such as meteorite impacts or global warfare - may send the planet
back into another glacial cycle - probably the last thing survivors will
Because of these risks - and because the benefits of increased global
temperatures are so great - an action plan
is proposed to melt the ice caps - and more rapidly increase the safety and
habitability of the planet.
Having said that, some fear that the current changes are taking place too
rapidly - and think we should slow progress in this area down, rather than
speeding it up. I am inclined to think that the case for this is weak. Slowing down leaves the planet frozen for longer, and extends the duration of the period in which the climate is changing.
- What about the idea that global warming could slow the north atlantic
current, cooling northern Europe, thereby precipitating a new ice age?
This idea is hogwash - it never made any scientific sense in the first place,
and has now been widely discredited. For details, see here.
- What about deserts? Aren't they as bad as ice sheets?
really - deserts can be dealt with by irrigation projects. There is no
planetary water shortage - but there are water distribution problems.
We need to continue to work on water distribution. Though a warmer planet will
cause faster evaporation of surface water, it will also help dramatically
in this area - by increasing precipitation. Warming will eliminate the world's
deserts. Deserts are an ice age phenomenon.
- Humans are not built to withstand high temperatures - what about
Most temperature increases will be far from the equator. Currently, regions
near the equator have some of the largest population densities. Consider India,
for example. Humans thrive in the conditions currently there. Even if
equatorial regions become less hospitable, this seems likely to be
compensated for by all the other gains elsewhere.
- What about costal flooding?
If we successfully melt the ice caps, sea levels will rise.
However, this will inevitably happen gradually - over many thousands of years.
There will be lots of time to get out of the way. Currently sea
levels are estimated to be rising at about 2mm per year: this is an
extremely slow rate of progress. My page on [Ocean reclamation]
indicates what will eventually happen to much of the ocean surface.
- What about the rainforests and the coral reefs?
At the moment, these are confined to equatorial regions. If the planet warms
up a bit, the areas which are capable of supporting this type of ecosystem
will expand substantially northwards and southwards.
- What about the idea that we will turn the Earth into a planet like
We are too far away from the sun for that to happen for a few billion years
There are some real environmental issues out there which need
addressing. The world badly needs proper irrigation. Heavy metals and
other pollutants degrade the environment.
I do not recommend wasting resources in a mostly-futile attempt to cool the planet down. That would put you on the side of those who want to drag the planet back into the dark ages.
I do not recommend demonizing carbon either. Carbon dioxide is plant fuel.
Plants thrive in CO2-rich atmospheres, grow faster, and absorb more
CO2. Some horticulturists pump CO2 into greenhouses to
encourage plant growth. Carbon is essential to all living things. Carbon
dioxide is good. Carbon sequestration would be an idiotic move.
The hysteria about global warming serves primarily to drain energy,
funds and time from more important issues. Global warming is a bad
cause. As such, it is mostly a destructive force. As with other
types of religous zealotry, the supporters are typically well meaning, but
Isn't the ice age already over?
No. The most recent glacial period has ended - but that's not usually
the end of the ice age. Laymen sometimes refer to the glacial periods
themselves as "ice ages" - but that is not how real scientists use the term.
Whether humanity's efforts to heat the planet will prove sufficient to end
the current ice age - despite the adverse continental positions -
remains to be seen.
One thing we can be pretty sure of: the costs of failing to end the ice
age will dwarf any side effects of over-zealousness in attempting to prevent
Warming up the planet will represent a substantial engineering challenge.
It may demand skills beyond our existing technological abilities.
However, its importance is very great.
Unless humans intervene on a dramatic scale and successfully end the
current ice age, there is a large probability that the planet will shortly be
plunged into yet another period of devastating glaciation, greatly reducing the
planet's habitable zone, and destroying many living things.
Once the planet enters another glaciation cycle, positive feedback effects
mean that it will may be very difficult to extricate it. In order to avoid
this fate - and to make the planet more habitable - we should work on heating
up the planet now.
Dyson on Global warming
Climate of Fear: Why We Shouldn't Worry About Global Warming, by Thomas Gale Moore
Harrison H. Schmitt and William Happer: In Defense of Carbon Dioxide
The Greening of Planet Earth (1992)
The Greening of Planet Earth Continues (1998)
Global Warming: A Chilling Perspective
Ice Age Now - "Not by Fire but by Ice"
Fossil-fuel hangover may block ice ages
Global Warming and Nature's Thermostat - an article on clouds
Global warming is good
Why climate change is good for the world - Matt Ridley
Global warming is good for you
GLOBAL WARMING: A Boon to Humans and Other Animals - from 1995
'World doing just fine; Global Warming is Good; CO2 is our friend' say Scientists
Glacier scientist: Global warming is good, not bad
Retired professor turns whistleblower on climate change
Love Global Warming - opinion piece
Global warming 'is good and is not our fault'
Global Warming a Boon for Greenland's Farmers
Global warming will save millions
Global warming will save millions of lives
Tyler, Tim Global greening
CO2 Science - Is carbon dioxide a harmful air pollutant, or is it an amazingly effective aerial fertilizer?
CO2 is green - Claims that CO2 is a pollutant are a myth and are absolutely false
Carbon Dioxide - The Miracle of Food
Climate of fear: why we shouldn't worry about global warming
Unstoppable Global Warming: Every 1,500 Years
Meltdown: The Predictable Distortion of Global Warming by Scientists, Politicians, and the Media
Climate of Extremes: Global Warming Science They Don't Want You to Know
The Satanic Gases: Clearing the Air about Global Warming
Relevant Wikipedia articles
Timeline of glaciation
Five Myr Climate Change
Effects of global warming
Mitigation of global warming
Adaptation to global warming
Carbon capture and storage
Scientific opinion on climate change
Global cooling - Concern in the mid-twentieth century
Do trees share blame for global warming?
A climate model suggests that chopping down the Earth's trees would help fight global warming
How Trees Might Not Be Green in Carbon Offsetting Debate
More Trees, Less Global Warming, Right? - Not Exactly
Gulf stream scare
The Source of Europe's Mild Climate
Gulf Stream Will Not Shut Down, Science Magazines Admit
No new ice age for western Europe
Gulf Stream safe if wind blows and Earth turns
The causes of ice ages - orbital inclination theories
A New Theory of Glacial Cycles
Spectrum of 100-kyr glacial cycle: Orbital inclination, not eccentricity - [PDF]
Glacial Cycles and Astronomical Forcing - 1997 summary
A brief introduction to ice age theories
The ice ages and the Earth's climate
Get Out Your Mittens
The causes of ice ages - solar cycle theories
Sun's fickle heart may leave us cold.
Solar resonant diffusion waves as a driver of terrestrial climate change [PDF].
The causes of ice ages - Milankovitch cycles
Long Debate Ended Over Cause, Demise Of Ice Ages? Research Into Earth's Wobble
New Scientist 'climate myths'
Climate myths: It's too cold where I live - warming will be great
Climate myths: Higher CO2 levels will boost plant growth and food production
Climate myths: It's been far warmer in the past, what's the big deal?
Global warming politics
Gore's climate film has scientific errors - judge
Gore and UN share Nobel peace prize