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NASA Study Finds World Warmth Edging Ancient Levels; 1° C Additional Warming Could Constitute Dangerous Change

Temperature change on average from 2001-2005. 2005 was the warmest ranked year on record. Dark red indicates the greatest warming and purple indicates the greatest cooling. Click image to enlarge. Credit: NASA

A new study by NASA climatologists finds that the world’s temperature is reaching a level that has not been seen in thousands of years.

Noting “that this critical ocean region [Western Pacific], and probably the planet as a whole, is approximately as warm now as at the Holocene maximum and within ~1°C of the maximum temperature of the past million years,” they conclude that additional global warming of more than 1° C relative to 2000 “will constitute dangerous climate change as judged from likely effects on sea level and extermination of species.

The study appears as an Open Access article in the current issue of the Proceedings of the National Academy of Sciences, authored by James Hansen of NASA’s Goddard Institute for Space Studies, N.Y. and colleagues from Columbia University, Sigma Space Partners, Inc., and the University of California at Santa Barbara (UCSB).

The study concludes that, because of a rapid warming trend over the past 30 years, the Earth is now reaching and passing through the warmest levels in the current interglacial period, which has lasted nearly 12,000 years. This warming is forcing a migration of plant and animal species toward the poles.

The study includes worldwide instrumental temperature measurements during the past century. These data reveal that the Earth has been warming at the remarkably rapid rate of approximately 0.2° Celsius (.36° Fahrenheit) per decade for the past 30 years. This observed warming is similar to the warming rate predicted in the 1980s in initial global climate model simulations with changing levels of greenhouse gases.

This evidence implies that we are getting close to dangerous levels of human-made pollution,” said Hansen. In recent decades, human-made greenhouse gases (GHGs) have become the dominant climate change factor.

The study notes that the world’s warming is greatest at high latitudes of the Northern Hemisphere, and it is larger over land than over ocean areas. The enhanced warming at high latitudes is attributed to effects of ice and snow. As the Earth warms, snow and ice melt, uncovering darker surfaces that absorb more sunlight and increase warming, a process called a positive feedback. Warming is less over ocean than over land because of the great heat capacity of the deep-mixing ocean, which causes warming to occur more slowly there.

Hansen and his colleagues in New York collaborated with David Lea and Martin Medina-Elizade of UCSB to obtain comparisons of recent temperatures with the history of the Earth over the past million years. The California researchers obtained a record of tropical ocean surface temperatures from the magnesium content in the shells of microscopic sea surface animals, as recorded in ocean sediments.

One of the findings from this collaboration is that the Western Equatorial Pacific and Indian Oceans are now as warm as, or warmer than, at any prior time in the Holocene. The Holocene is the relatively warm period that has existed for almost 12,000 years, since the end of the last major ice age. The Western Pacific and Indian Oceans are important because, as these researchers show, temperature change there is indicative of global temperature change. Therefore, by inference, the world as a whole is now as warm as, or warmer than, at any time in the Holocene.

According to Lea, “The Western Pacific is important for another reason, too: it is a major source of heat for the world’s oceans and for the global atmosphere.

In contrast to the Western Pacific, the researchers find that the Eastern Pacific Ocean has not shown an equal magnitude of warming. They explain the lesser warming in the East Pacific Ocean, near South America, as being due to the fact this region is kept cool by upwelling, rising of deeper colder water to shallower depths. The deep ocean layers have not yet been affected much by human-made warming.

Hansen and his colleagues suggest that the increased temperature difference between the Western and Eastern Pacific may boost the likelihood of strong El Niños, such as those of 1983 and 1998. An El Niño is an event that typically occurs every several years when the warm surface waters in the West Pacific slosh eastward toward South America, in the process altering weather patterns around the world.

The most important result found by these researchers is that the warming in recent decades has brought global temperature to a level within about one degree Celsius (1.8° F) of the maximum temperature of the past million years.

That means that further global warming of 1 degree Celsius defines a critical level. If warming is kept less than that, effects of global warming may be relatively manageable. During the warmest interglacial periods the Earth was reasonably similar to today. But if further global warming reaches 2 or 3 degrees Celsius, we will likely see changes that make Earth a different planet than the one we know. The last time it was that warm was in the middle Pliocene, about three million years ago, when sea level was estimated to have been about 25 meters (80 feet) higher than today.

—James Hansen

Global warming is already beginning to have noticeable effects in nature. Plants and animals can survive only within certain climatic zones, so with the warming of recent decades many of them are beginning to migrate poleward. A study that appeared in Nature Magazine in 2003 found that 1,700 plant, animal and insect species moved poleward at an average rate of 6 kilometers (about 4 miles) per decade in the last half of the 20th century.

That migration rate is not fast enough to keep up with the current rate of movement of a given temperature zone (isotherm), which has reached about 40 kilometers (about 25 miles) per decade in the period 1975 to 2005.

Inference of imminent dangerous climate change may stimulate discussion of “engineering fixes” to reduce global warming. The notion of such a “fix” is itself dangerous if it diminishes efforts to reduce CO2 emissions, yet it also would be irresponsible not to consider all ways to minimize climate damage. Considering the evidence that aerosol effects on clouds cause a large negative forcing, we suggest that seeding of clouds by ships plying selected ocean regions deserves investigation. However, given that a large portion of human-made CO2 will remain in the air for many centuries, sensible policies must focus on devising energy strategies that greatly reduce CO2 emissions.

—The Authors


  • “Global temperature change”; James Hansen, Makiko Sato, Reto Ruedy, Ken Lo, David W. Lea, and Martin Medina-Elizade; PNAS, published online Sep 25, 2006; doi:10.1073/pnas.0606291103



I hope all these estimates( in earlier postings) of power usage have considered the use of LED illumination. By changing from incandescent, halogen and fluorescent globes to LED lights the power usage can be reduced by up to 80%. The life (>50,000 hours) of LED lights is far greater than incandescent, Halogen (4000 - 10,000 hours)or fluorescent, and there is minimal heat produced. Importantly, the environment is not polluted by dangerous mercury as occurs when fragile fluorescent tubes break. The use of PV and LED lights is a great combination since there is no need to transform the voltage to mains voltage.
In fact, the dc to ac inverters are too unreliable (some manufacturers will not warrant inverters) and it would be better to use low voltage motors in appliances and not convert to mains voltage. Also, by wiring the home with low voltage would allow eliminate the use of wasteful power packs converting from mains to low voltage to drive computers, modems, LCD TV's, printers, etc. Further, it would remove the need to use expensive licenced electricians (especially in those countries using 230/240 volt mains) to wire up houses. Sure it would use more copper in the home, but less copper in massive transformers and high voltage transmission lines


Human made global warming is THE biggest scam. Even if true, nothing can be done - so, learn to live with the consequences. The plain truth is humans have insignifcant impact on this vast universe - we still have too much to understand how it works. IMO, to think otherwise is pretty naive.

However, I do support developing sustainable energy sources for other reasons (that is why I check this site often), but global warming is not one of them.


pathetic little troll,

your behaviour is typical of some of the global warming scam pushers


You are right. LEDs lighting is 10 times more efficient then incandescent bulb. Developed countries spend whopping 30% of their electricity on lighting. My opinion is that we are at the brink of energy revolution, and the key words are – LED and PHEV. However, both technologies are not matured enough for immediate implementation. Widely advertised useful life of LEDs is true for monochromatic LEDs – blue, green, red, etc. In order to emit white light (which is mix of all colors), short wavelength of blue LED is channeled to activate luminescence of phosphorus-based component, found in white LEDs. Its efficiency is smaller, and useful life 10 times shorter then monochromatic LEDs. Yet it is more expensive. This is the reason we do not see widespread of white LEDs for basic lighting. Biggest companies worldwide spend billions of dollars to solve this problem, and progress is very quick. Noshia and Lumiled are the leaders. This technology is so promising, then entire market of LED developers is bought-out, and no public traded company is working in this field.

Global Worming:
Human activity contributes barely 5% to natural carbon cycle, to GHG cycle even less. Transportation accounts for 20% of this 5%, passenger cars being about half of it. If we manage magically to reduce fuel consumed by cars – in whole world, include booming China and India - by 10%, we will offset only 1part of global carbon uptake of 2000 parts. There are researches that increase in atmospheric CO2 concentration is result of warmer weather, not the reason for it. Any way, if we are serious about controlling of climate for whatever reason – antropogenic or cosmic, we have to concentrate on 2000 parts of carbon uptake, not 1 part. That effectively means biological carbon sequestration, first of all ocean fertilization but there are another biological means to achieve this. Unfortunately, this approach will not give to ACTIVE proponents of Kyoto or alike measures what they really seek – immediate and huge monetary resources to control and redistribute, such as carbon tax and the easiest prey – personal transportation.

P.S. I do believe that efficient energy use, alternative fuels, energy independence, clean and efficient transportation, etc. – are ever important to all of us and should be aggressively pursued, no matter GW or not.


"Human activity contributes barely 5% to natural carbon cycle, to GHG cycle even less." - this is largely irrelevant to the phenomenon (for now) because we know that it is only this 5% that is pushing up recent CO2 concentrations (clearly shown through isotope analysis). So assuming your other estimates are correct Andrey, by reducing car CO2 emissions by 10% we would cut the causes of current warming by 1% not 0.05%. It is no secret that coal is the major worry as far as global warming is concerned. It is after the feedback tipping points, ie melting of permafrost, that our contribution may become less important and it is for this reason that it is so urgent that we do something now while we still can. You can sit there and say its hopeless Andrey but I don't think that is helping the situation much.


Andrey wrote: Human activity contributes barely 5% to natural carbon cycle, to GHG cycle even less.

You're confusing two things here: gross vs net, and timescale. That 5% contribution (it's actually more like 2-3%) is our contribution to the gross carbon flux to the atmosphere. It is 100% of the net flux, because the rest of the system is in ~equilibrium. The oceans may release 90 Gtons C to the atmosphere every year, but take up 92. Soils release 60 Gtons C/yr but take up 60. Our contribution is a perturbation to a system in dynamic equilibrium.

The reason we're a perturbation, that is, that a new equilibrium hasn't been reached, is timescale. Our CO2 emissions accelerated tremendously starting about 150 years ago (and is still climbing). One of the major sinks of atmospheric carbon is the deep ocean, which is quite undersaturated with respect to CO2; however, the ocean turnover time is about 400 years, so we're putting out the stuff faster than it can be accommodated. As a result, it piles up in the atmosphere.

You might say that our additional carbon contribution is still small, in the big picture. That's fine. If there were no CO2 and other GHGs, this place would be an iceball, so some greenhouse warming is good (of course it hardly follows that more would be better). And after all, we're only talking about a few degrees increase in the global mean temperature. We as a species have survived conditions where global mean temperatures were several degrees colder and can do so again, if necessary; quite likely we can adapt to higher temperatures as well. But the transition to getting there will be ugly, violent, and will likely require a significant "adjustment" in population. The issues here are minimizing the magnitude of that transition and extending its timescale.


Thanks for a nice clarification dt.


DT, Marcus:
Carbon cycle does not distinguish natural and anthropogenic CO2. Plants and oceans adsorb both. And as any system in equilibrium, it is in quasi-stable equilibrium, i.e. it resists any changes before they become too large. Increasing CO2 concentration in atmosphere suggests that this equilibrium is moving, but modern science even remotely could not prove that it is human activity which trip the scale, neither we approaching run-away point or not.

But it was not my point. It looks like we can not decrease anyhow substantially our input of CO2 – for many reasons. My point is that it is way more realistic and cost effective to concentrate on another part of the equation – increase carbon sink (by biological means)of ALL CO2 in atmosphere, if the problem appears so dramatic. This way we will be theoretically able not only slightly decrease our carbon input – max what we possibly hope to achieve by Kyoto-like measures, but even compensate in future for undesirable (from human point of view) climate change derived from natural factors – sun radiation fluctuation, climate cycles, etc.


Carbon cycle does not distinguish natural and anthropogenic CO2. Plants and oceans adsorb both.

Quite so, but to dismiss a 5% (again, more like half that) contribution to the gross flux misses the point. The carbon cycle has been in ~equilibrium for millennia at an atmopsheric concentration of ~280 ppm until about 150 years ago. Now, anything that added more atmospheric carbon without a matching sink term would lead to the increase in CO2 we observe. It could have been a massive increase in volcanic activity, very rapid tectonic motion, a marked change biological activity, whatever. In the event, the only thing we've been able to identify that has changed dramatically is biological activity: digging up and burning fossil fuels.

The good news is that we have the power to change this. If the additional CO2 forcing were from changes in the rock cycle, we'd be screwed -- we've no control over that. If it had come from a sudden rain of carbonaceous meteorites, we'd be screwed -- we've no control over that. Same for sudden overturning of the oceans. But fossil fuel use and land use changes -- we can control those.

And as any system in equilibrium, it is in quasi-stable equilibrium, i.e. it resists any changes before they become too large.

That's actually a characteristic of a system with negative feedback. Equilibrium doesn't imply stability.

Increasing CO2 concentration in atmosphere suggests that this equilibrium is moving, but modern science even remotely could not prove that it is human activity which trip the scale, neither we approaching run-away point or not.

There is nothing else that has changed enough in the last 150 years to account for the rapid increase of atmospheric carbon. There are a great many things that can affect CO2 levels, but not to consider anthropogenic forcing is to avoid acknowledging the elephant in the room.


For a good explanation and discussion on this topic see here:




Climate began to warm-up about 3 hundred years ago, CO2 concentration began to increase about 150 years ago, massive combustion of fossil fuel began about 50 years ago. Yet we are paranoidally fixed only on reduction of fossil fuel combustion. Seems of questionable value to me.

P.S.: each year, as more data is unveiled, part of antropogenic carbon in global carbon balance is reduced. I refer to not-up-to-date data with upper safety bracket, so your number of 2-3% is probably closer to real one.


Climate began to warm-up about 3 hundred years ago

Uh... no.


Try this

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