NASA Chief Questions Urgency of Global Warming

[Master Zen]

Originally posted by rah
It seems no one want to discuss that openly. It's happening and that makes it automatically bad. It may be, but I am far from convinced of that and the people that assume that without questioning it scare me.

So it's good?

[Ogie Oglethorpe]

Originally posted by lord of the mark
Within certain parameters, we CAN project the trajectory of the climate.

Not really.


We know its increasing but thats about it. Until positive or negative effects of the dominating variable water vapor/cloud cover is understood we're spitting in the wind.

[Ogie Oglethorpe]

Originally posted by Master Zen


So it's good?

A case can be made for it being good. Increased CO2, temperatures and rain fall expected from warmer overall climes mean greater vegetative growth. Retreat of glaciers mean more habitable lands in high latitude/altitude areas.

All in all much better than say glacialization associated with ice ages.

Balance that against regional drought afflicted areas, potential storm increases, flooded areas, and loss of ecodiversity etc. (gulf stream shut down and other sundry doomsday scenarios)

[Slade Wilson]

Global Warmers are constantly trying to railroad the issue and anyone that doesn't comply is treated like they are denying something that has been proven. Its alot of mass hysteria, irregardless of whether global warming is real or not and if its a problem

[lord of the mark]

"Analysis of climate models together with constraints from observations enables an assessed likely range
to be given for climate sensitivity for the first time and provides increased confidence in the
understanding of the climate system response to radiative forcing. {6.6, 8.6, 9.6, Box 10.2}
• The equilibrium climate sensitivity is a measure of the climate system response to sustained radiative forcing.
It is not a projection but is defined as the global average surface warming following a doubling of carbon
dioxide concentrations. It is likely to be in the range 2 to 4.5°C with a best estimate of about 3°C, and is very
unlikely to be less than 1.5°C. Values substantially higher than 4.5°C cannot be excluded, but agreement of
models with observations is not as good for those values. Water vapour changes represent the largest feedback
affecting climate sensitivity and are now better understood than in the TAR. Cloud feedbacks remain the
largest source of uncertainty. {8.6, 9.6, Box 10.2}



"PROJECTIONS OF FUTURE CHANGES IN CLIMATE
A major advance of this assessment of climate change projections compared with the TAR is the large number of
simulations available from a broader range of models. Taken together with additional information from observations,
these provide a quantitative basis for estimating likelihoods for many aspects of future climate change. Model
simulations cover a range of possible futures including idealised emission or concentration assumptions. These include
SRES14 illustrative marker scenarios for the 2000–2100 period and model experiments with greenhouse gases and
aerosol concentrations held constant after year 2000 or 2100.
For the next two decades a warming of about 0.2°C per decade is projected for a range of SRES
emission scenarios. Even if the concentrations of all greenhouse gases and aerosols had been kept
constant at year 2000 levels, a further warming of about 0.1°C per decade would be expected. {10.3,
10.7}
13 In particular, the Southern and Northern Annular Modes and related changes in the North Atlantic Oscillation. {3.6, 9.5, Box TS.3.1}
14 SRES refers to the IPCC Special Report on Emission Scenarios (2000). The SRES scenario families and illustrative cases, which did not
include additional climate initiatives, are summarized in a box at the end of this Summary for Policymakers. Approximate CO2 equivalent
concentrations corresponding to the computed radiative forcing due to anthropogenic greenhouse gases and aerosols in 2100 (see p. 823 of the
TAR) for the SRES B1, A1T, B2, A1B, A2 and A1FI illustrative marker scenarios are about 600, 700, 800, 850, 1250 and 1550 ppm
respectively. Scenarios B1, A1B, and A2 have been the focus of model inter-comparison studies and many of those results are assessed in this
report.
Summary for Policymakers IPCC WGI Fourth Assessment Report
Page 13 of 18
• Since IPCC’s first report in 1990, assessed projections have suggested global averaged temperature increases
between about 0.15 and 0.3°C per decade for 1990 to 2005. This can now be compared with observed values
of about 0.2°C per decade, strengthening confidence in near-term projections. {1.2, 3.2}
• Model experiments show that even if all radiative forcing agents are held constant at year 2000 levels, a
further warming trend would occur in the next two decades at a rate of about 0.1°C per decade, due mainly to
the slow response of the oceans. About twice as much warming (0.2°C per decade) would be expected if
emissions are within the range of the SRES scenarios. Best-estimate projections from models indicate that
decadal-average warming over each inhabited continent by 2030 is insensitive to the choice among SRES
scenarios and is very likely to be at least twice as large as the corresponding model-estimated natural
variability during the 20th century. {9.4, 10.3, 10.5, 11.2–11.7, Figure TS-29}
Continued greenhouse gas emissions at or above current rates would cause further warming and
induce many changes in the global climate system during the 21st century that would very likely be
larger than those observed during the 20th century. {10.3}
• Advances in climate change modelling now enable best estimates and likely assessed uncertainty ranges to be
given for projected warming for different emission scenarios. Results for different emission scenarios are
provided explicitly in this report to avoid loss of this policy-relevant information. Projected globally-averaged
surface warmings for the end of the 21st century (2090–2099) relative to 1980–1999 are shown in Table
SPM-3. These illustrate the differences between lower to higher SRES emission scenarios and the projected
warming uncertainty associated with these scenarios. {10.5}
• Best estimates and likely ranges for globally average surface air warming for six SRES emissions marker
scenarios are given in this assessment and are shown in Table SPM-3. For example, the best estimate for the
low scenario (B1) is 1.8°C (likely range is 1.1°C to 2.9°C), and the best estimate for the high scenario (A1FI)
is 4.0°C (likely range is 2.4°C to 6.4°C). Although these projections are broadly consistent with the span
quoted in the TAR (1.4 to 5.8°C), they are not directly comparable (see Figure SPM-5). The AR4 is more
advanced as it provides best estimates and an assessed likelihood range for each of the marker scenarios. The
new assessment of the likely ranges now relies on a larger number of climate models of increasing complexity
and realism, as well as new information regarding the nature of feedbacks from the carbon cycle and
constraints on climate response from observations. {10.5}
Table SPM-3. Projected globally averaged surface warming and sea level rise at the end of the 21st century. {10.5, 10.6,
Table 10.7}
Temperature Change
(°C at 2090-2099 relative to 1980-1999) a
Sea Level Rise
(m at 2090-2099 relative to 1980-1999)
Case Best
estimate
Likely
range
Model-based range
excluding future rapid dynamical
changes in ice flow
Constant Year 2000
concentrations b 0.6 0.3 – 0.9 NA
B1 scenario 1.8 1.1 – 2.9 0.18 – 0.38
A1T scenario 2.4 1.4 – 3.8 0.20 – 0.45
B2 scenario 2.4 1.4 – 3.8 0.20 – 0.43
A1B scenario 2.8 1.7 – 4.4 0.21 – 0.48
A2 scenario 3.4 2.0 – 5.4 0.23 – 0.51
A1FI scenario 4.0 2.4 – 6.4 0.26 – 0.59
Table notes:
a These estimates are assessed from a hierarchy of models that encompass a simple climate model, several Earth Models of
Intermediate Complexity (EMICs), and a large number of Atmosphere-Ocean Global Circulaion Models (AOGCMs).
b Year 2000 constant composition is derived from AOGCMs only.
Summary for Policymakers IPCC WGI Fourth Assessment Report
Page 14 of 18
FIGURE SPM-5. Solid lines are multi-model global averages of surface warming (relative to 1980-99) for the scenarios
A2, A1B and B1, shown as continuations of the 20th century simulations. Shading denotes the plus/minus one standard
deviation range of individual model annual averages. The orange line is for the experiment where concentrations were
held constant at year 2000 values. The gray bars at right indicate the best estimate (solid line within each bar) and the
likely range assessed for the six SRES marker scenarios. The assessment of the best estimate and likely ranges in the gray
bars includes the AOGCMs in the left part of the figure, as well as results from a hierarchy of independent models and
observational constraints. {Figures 10.4 and 10.29}
• Warming tends to reduce land and ocean uptake of atmospheric carbon dioxide, increasing the fraction of
anthropogenic emissions that remains in the atmosphere. For the A2 scenario, for example, the climate-carbon
cycle feedback increases the corresponding global average warming at 2100 by more than 1°C. Assessed
upper ranges for temperature projections are larger than in the TAR (see Table SPM-3) mainly because the
broader range of models now available suggests stronger climate-carbon cycle feedbacks. {7.3, 10.5}
• Model-based projections of global average sea level rise at the end of the 21st century (2090-2099) are shown
in Table SPM-3. For each scenario, the midpoint of the range in Table SPM-3 is within 10% of the TAR
model average for 2090-2099. The ranges are narrower than in the TAR mainly because of improved
information about some uncertainties in the projected contributions15. {10.6}
• Models used to date do not include uncertainties in climate-carbon cycle feedback nor do they include the full
effects of changes in ice sheet flow, because a basis in published literature is lacking. The projections include
a contribution due to increased ice flow from Greenland and Antarctica at the rates observed for 1993-2003,
but these flow rates could increase or decrease in the future. For example, if this contribution were to grow
15 TAR projections were made for 2100, whereas projections in this Report are for 2090-2099. The TAR would have had similar ranges to those
in Table SPM-2 if it had treated the uncertainties in the same way.
Summary for Policymakers IPCC WGI Fourth Assessment Report
Page 15 of 18
linearly with global average temperature change, the upper ranges of sea level rise for SRES scenarios shown
in Table SPM-3 would increase by 0.1 m to 0.2 m. Larger values cannot be excluded, but understanding of
these effects is too limited to assess their likelihood or provide a best estimate or an upper bound for sea level
rise. {10.6}
• Increasing atmospheric carbon dioxide concentrations leads to increasing acidification of the ocean.
Projections based on SRES scenarios give reductions in average global surface ocean pH16 of between 0.14
and 0.35 units over the 21st century, adding to the present decrease of 0.1 units since pre-industrial times.
{5.4, Box 7.3, 10.4}
There is now higher confidence in projected patterns of warming and other regional-scale features,
including changes in wind patterns, precipitation, and some aspects of extremes and of ice. {8.2, 8.3,
8.4, 8.5, 9.4, 9.5, 10.3, 11.1}
• Projected warming in the 21st century shows scenario-independent geographical patterns similar to those
observed over the past several decades. Warming is expected to be greatest over land and at most high
northern latitudes, and least over the Southern Ocean and parts of the North Atlantic ocean (see Figure SPM-
6). {10.3}
FIGURE SPM-6. Projected surface temperature changes for the early and late 21st century relative to the period 1980–
1999. The central and right panels show the Atmosphere-Ocean General Circulation multi-Model average projections for
the B1 (top), A1B (middle) and A2 (bottom) SRES scenarios averaged over decades 2020–2029 (center) and 2090–2099
(right). The left panel shows corresponding uncertainties as the relative probabilities of estimated global average warming
from several different AOGCM and EMICs studies for the same periods. Some studies present results only for a subset of
the SRES scenarios, or for various model versions. Therefore the difference in the number of curves, shown in the lefthand
panels, is due only to differences in the availability of results. {Figures 10.8 and 10.28}
16 Decreases in pH correspond to increases in acidity of a solution. See Glossary for further details.
Summary for Policymakers IPCC WGI Fourth Assessment Report
Page 16 of 18
• Snow cover is projected to contract. Widespread increases in thaw depth are projected over most permafrost
regions. {10.3, 10.6}
• Sea ice is projected to shrink in both the Arctic and Antarctic under all SRES scenarios. In some projections,
Arctic late-summer sea ice disappears almost entirely by the latter part of the 21st century. {10.3}
• It is very likely that hot extremes, heat waves, and heavy precipitation events will continue to become more
frequent. {10.3}
• Based on a range of models, it is likely that future tropical cyclones (typhoons and hurricanes) will become
more intense, with larger peak wind speeds and more heavy precipitation associated with ongoing increases of
tropical SSTs. There is less confidence in projections of a global decrease in numbers of tropical cyclones.
The apparent increase in the proportion of very intense storms since 1970 in some regions is much larger than
simulated by current models for that period. {9.5, 10.3, 3.8}
• Extra-tropical storm tracks are projected to move poleward, with consequent changes in wind, precipitation,
and temperature patterns, continuing the broad pattern of observed trends over the last half-century. {3.6,
10.3}
• Since the TAR there is an improving understanding of projected patterns of precipitation. Increases in the
amount of precipitation are very likely in high-latitudes, while decreases are likely in most subtropical land
regions (by as much as about 20% in the A1B scenario in 2100, see Figure SPM-7), continuing observed
patterns in recent trends. {3.3, 8.3, 9.5, 10.3, 11.2 to 11.9}
• Based on current model simulations, it is very likely that the meridional overturning circulation (MOC) of the
Atlantic Ocean will slow down during the 21st century. The multi-model average reduction by 2100 is 25%
(range from zero to about 50%) for SRES emission scenario A1B. Temperatures in the Atlantic region are
projected to increase despite such changes due to the much larger warming associated with projected
increases of greenhouse gases. It is very unlikely that the MOC will undergo a large abrupt transition during
the 21st century. Longer-term changes in the MOC cannot be assessed with confidence. {10.3, 10.7}
FIGURE SPM-7. Relative changes in precipitation (in percent) for the period 2090–2099, relative to 1980–1999. Values
are multi-model averages based on the SRES A1B scenario for December to February (left) and June to August (right).
White areas are where less than 66% of the models agree in the sign of the change and stippled areas are where more than
90% of the models agree in the sign of the change. {Figure 10.9}
Summary for Policymakers IPCC WGI Fourth Assessment Report
Page 17 of 18
Anthropogenic warming and sea level rise would continue for centuries due to the timescales
associated with climate processes and feedbacks, even if greenhouse gas concentrations were to be
stabilized. {10.4, 10.5, 10.7}
• Climate carbon cycle coupling is expected to add carbon dioxide to the atmosphere as the climate system
warms, but the magnitude of this feedback is uncertain. This increases the uncertainty in the trajectory of
carbon dioxide emissions required to achieve a particular stabilisation level of atmospheric carbon dioxide
concentration. Based on current understanding of climate carbon cycle feedback, model studies suggest that to
stabilise at 450 ppm carbon dioxide, could require that cumulative emissions over the 21st century be reduced
from an average of approximately 670 [630 to 710] GtC (2460 [2310 to 2600] GtCO2) to approximately 490
[375 to 600] GtC (1800 [1370 to 2200] GtCO2). Similarly, to stabilise at 1000 ppm this feedback could
require that cumulative emissions be reduced from a model average of approximately 1415 [1340 to 1490]
GtC (5190 [4910 to 5460] GtCO2) to approximately 1100 [980 to 1250] GtC (4030 [3590 to 4580] GtCO2).
{7.3, 10.4}
• If radiative forcing were to be stabilized in 2100 at B1 or A1B levels11 a further increase in global average
temperature of about 0.5°C would still be expected, mostly by 2200. {10.7}
• If radiative forcing were to be stabilized in 2100 at A1B levels11, thermal expansion alone would lead to 0.3 to
0.8 m of sea level rise by 2300 (relative to 1980–1999). Thermal expansion would continue for many
centuries, due to the time required to transport heat into the deep ocean. {10.7}
• Contraction of the Greenland ice sheet is projected to continue to contribute to sea level rise after 2100.
Current models suggest ice mass losses increase with temperature more rapidly than gains due to precipitation
and that the surface mass balance becomes negative at a global average warming (relative to pre-industrial
values) in excess of 1.9 to 4.6°C. If a negative surface mass balance were sustained for millennia, that would
lead to virtually complete elimination of the Greenland ice sheet and a resulting contribution to sea level rise
of about 7 m. The corresponding future temperatures in Greenland are comparable to those inferred for the
last interglacial period 125,000 years ago, when paleoclimatic information suggests reductions of polar land
ice extent and 4 to 6 m of sea level rise. {6.4, 10.7}
• Dynamical processes related to ice flow not included in current models but suggested by recent observations
could increase the vulnerability of the ice sheets to warming, increasing future sea level rise. Understanding
of these processes is limited and there is no consensus on their magnitude. {4.6, 10.7}
• Current global model studies project that the Antarctic ice sheet will remain too cold for widespread surface
melting and is expected to gain in mass due to increased snowfall. However, net loss of ice mass could occur
if dynamical ice discharge dominates the ice sheet mass balance. {10.7}
• Both past and future anthropogenic carbon dioxide emissions will continue to contribute to warming and sea
level rise for more than a millennium, due to the timescales required for removal of this gas from the
atmosphere. {7.3, 10.3}

[Slade Wilson]

And next week a doctor with a flashlight shows us where sales projections come from

Dire predictions for the future have been issued since the ''invention'' of predictions. Whats the source on that?

[Flubber]

Originally posted by rah
Hmmm



I didn't see anyone in this thread denying that global warming exists.
I see someone asking is it best to slow it. It seems no one want to discuss that openly. It's happening and that makes it automatically bad. It may be, but I am far from convinced of that and the people that assume that without questioning it scare me. They're just as stuborn as the people that claim it doesn't exist.

I'm similar-- I fear the bandwagon regardless of the issue. The majority on a topic may be totally correct but that doesn't mean that it stops being healthy to question and test that majority view.

On global warming, I would not choose to dispute two facts

1. Our planet is on average getting warmer.

2. Human emissions are contributing to that warming.

But when it comes to the projections for future warming or cooling, the level of causation of various factors, and the likely impacts , there seems to be far less facts and knowledge and far more conjecture. The reality is that we have simply not done enough science in the past on the issue to fully understand.

I read a scientific paper about water temperatures off Atlantic Canada. I read it because the water temperatures in 2005 had hit some recent highs and people were citing it as evidence of global warming impacts. But the underlying research was more complex. Here's the abstract

A review of decadal changes in the ocean climate in NAFO waters adjacent to Newfoundland and Labrador is presented based on standard station and section data and data from fishery resource assessment surveys. Both the annual trends and decadal means are examined for the decades of the 1950s to the 1990s. The analysis indicates that the 1950s and particularly the 1960s were the warmest decades during the latter half of the 20th century and the 1990s represent the third consecutive decade with below normal temperatures on the Newfoundland Shelf. The decadal mean salinity indicate that the magnitude of negative salinity anomaly on the inner Newfoundland Shelf during the 1990s was comparable to that experienced during the 'Great Salinity Anomaly' of the early 1970s. In addition, the decade of the 1990s has experienced some of the most extreme variations since measurements began during the mid-1940s. Ocean temperatures ranged from record low values during 1991 to record highs during 1999 in many areas, particularly on the Grand Bank of Newfoundland. The potential impact of the changes in ocean climate during the past several decades on marine production in Newfoundland waters is discussed

http://journal.nafo.int/34/colbourne/4-colbourne.html

So the history is warm-cold- warm as general trends over the last 50 years with some worrying rapid change in the 90s. Does this prove anything at all either way about global warming? Probably very little without correlation to a lot more data

MY point? There were numerous stories that pointed to the water temperature highs in this area in 2005 as "evidence" of global warming. It was a story on CBS.com for instance --- and perhaps it is . .. But since the previous highs were in the 50s and 60s with cooling in the 70s and 80s, it would seem that you would have to explain those phenomenon before you could really make the global warming causation assertion with some certainty. BUt most people don't bother with that.

Its similar to when I see headlines that say "2006 warmest year" when there is solid evidence that the Planet has been warmer at other points in its history. It seems the media grabs on to some statistic and go to town with it and most of the population hardly glances at the details. But with this stuff the devil is in the details.

I am not a denyer by any stretch and I think this world has many huge environmental problems to tackle. I am just not certain that this focus on CO2 to yhr aslmost exclusion of all else is warranted. It would be nioce to see something more done about landfills, sulfur emissions, dirty coal, air quality, water quality.

Why the possibility of a sea rise in 50 years gets all the attention while the FACT that in many cities the air is pretty much unfit to breathe, frankly boggles my mind

[Ogie Oglethorpe]

LotM,

That is huge variability. I don't call that a reliable prediction by any stretch.


If thats the best they can do and it was back in 2006 when I was following it then Christy was correct in saying we can not reliably predict the trajectory.

Again water vapor effects especially albedo effects of clouds remain the largest unknown. Seems as though that still remains the nut to crack even today.

[lord of the mark]

If it were just a few anecdotal reports in the press, Id be with you flubber.


On the other hand if that was all we had, Id suggest that the money we've been spending on climate modeling, research etc has been wasted.

For over 20 years now global warming skeptics have suggested that we dont have enough research. Well, we've been doing research, as they suggested, and we know much more about the climate then we did before. This isnt a bandwagon, its learning. Thats how science advances.

Of course its fine if someone wants to keep testing the original question. Whats wrong is to assume that we dont know a great deal about the likely magnitude of impacts. Or to have congressmen make it look like theres no consensus.

Again, there was questioning (rightly so) of the germ theory of disease for a long time - but we began taking public health measures based on that theory without waiting for 100% agreement.

[Ogie Oglethorpe]

Why the possibility of a sea rise in 50 years gets all the attention while the FACT that in many cities the air is pretty much unfit to breathe, frankly boggles my mind

But its those same cities that have spew out soot and particulates that help keep the planet cool.

China good

US complying with 1990 clean air act and the West in general bad

[lord of the mark]

Originally posted by Ogie Oglethorpe
LotM,

That is huge variability. I don't call that a reliable prediction by any stretch.


If thats the best they can do and it was back in 2006 when I was following it then Christy was correct in saying we can not reliably predict the trajectory.

Again water vapor effects especially albedo effects of clouds remain the largest unknown. Seems as though that still remains the nut to crack even today.

"It is likely to be in the range 2 to 4.5°C with a best estimate of about 3°C, and is very
unlikely to be less than 1.5°C. "

I think thats a far narrower range than some congressmen are likely to take away from the Christy statement. I think they are likely to take the Christy statement as indicating that zero change is within the realm of possibilty. Even 1.5degree C change is, IIUC, enough to have dramatic changes on earth systems, and in turn, dramatic social, economic and other impacts. Id much rather that the policy makers simply took the low estimate and started examining the implications, then that they say "Well we dont know" and use that as an excuse to defer action.

Simarly, I presume the low end estimate reflects the best case (IE least warming case) wrt to the impact of clouds. Which is not necessarily the most likely case given what we know now.

It seems that theres a constant refrain of "we are not certain" ergo "we dont know anything" ergo "we must not act"

which to me is intellectually dishonest. Whether as individuals, or as policy makers, we constantly make decisions based on the best info available at the moment. We have no choice, because to not act is also an action, one that can have irreversible consequences.

[lord of the mark]

Originally posted by Flubber

Why the possibility of a sea rise in 50 years gets all the attention while the FACT that in many cities the air is pretty much unfit to breathe, frankly boggles my mind

For the last 40 years we've been arguing over, and addressing conventional air pollution. Its still a major factor in public policy here in the states.

Im not quite sure what youre talking about. Air quality in China? Quite frankly thats Chinas problem. GHG, on the other hand, is an international problem (of course acid rain is an international problem too, between neighboring countries, but Canadas stealth nation tech makes it possible to overlook that issue)

[Flubber]

Now even if it were absolutely proven that human caused global warming did NOT exist today (just assume it for a moment) I would still be generally in favor of every country trying to cut their various emissions. CO2 is very rarely emitted alone and is often accompanied by much more nasty substances. So absent global warming, it would still be a very very good idea to start trying the reduc we litter our planet withe the amount of crap

[lord of the mark]

Originally posted by Flubber
Now even if it were absolutely proven that human caused global warming did NOT exist today (just assume it for a moment) I would still be generally in favor of every country trying to cut their various emissions. CO2 is very rarely emitted alone and is often accompanied by much more nasty substances. So absent global warming, it would still be a very very good idea to start trying the reduc we litter our planet withe the amount of crap

But that would be a domestic issue, not an international one, and the policies would be different. The US has long had policies under the clean air acts to reduce SO2, NO2, CO, and particulates. But you can clean those up without addressing GHG.

[lord of the mark]

Here, BTW, is a study suggesting that rainfall patterns are already changing.

http://news.yahoo.com/s/afp/20070723/sc_afp/climatewarmingweather_070723130614