Climate Change Impacts In The USA are Already (NOT) Happening

by Craig Loehle, Ph.D.

Many government reports by NASA, NOAA, EPA, USFWS, USFS, USDA and other agencies mention that climate change impacts are already observable in the USA. This is discussed in the context of endangered species conservation, forest resource assessment, future water availability, disaster planning, agriculture policy, etc. I have read many of these reports, which often refer back to the IPCC or the US Global Change Research Program. But they are usually vague on details of what bad things are expected to happen, generally referring to increases in extreme events. Nevertheless, these vague bad things are being used to guide policy.

The USA has some of the best data and is a large country. Are bad effects of climate change really visible already? In what follows, I address the evidence often put forward to support these claims and compare these to the literature. The true story is far from alarming.

Ocean Acidification

One government draft report indicated that ocean pH has decreased (become more acid) by 0.1 units, and that this represents a 30% increase in acidity since 1750. Because pH is a log scale, estimating percent increases in acidity is problematic and a change of 0.1 units could not represent a 30% change in acidity as stated. A serious issue not addressed by the report is that a global time series of pH data for the oceans does not exist. Thus, the provenance of the 0.1 unit change in value is dubious, and the confidence intervals on such an estimate would no doubt be large. Furthermore, daily, seasonal, and between year pH fluctuations at any given location are on the order of ±0.3 pH units or more (Middelboe and Hansen 2007; Pelejero et al. 2005).

Sea Level Rise

Some reports state that sea level rise poses a threat to United States natural habitats, with other reports focusing on risks to developed areas. According to the Intergovernmental Panel on Climate Change (IPCC) temperatures due to human activity began to rise after 1980, but estimates of sea level show a rise from about 1870 (earliest records) at a nearly linear rate and with no sign of acceleration. Sea level rise from 1870 to 1980 is not likely due to human activity. One report indicates that IPCC has projected a sea level rise of 0.4 to 2 m by 2090, but the fourth IPCC report does not make such a claim, instead giving a best estimate of 0.28 to 0.43 m. Recent levels of rise (, at 3.1 mm/year long-term trend or 0.31 m in 100 years with no indication of “acceleration,” are only consistent with the lowest IPCC projections. In fact, recent deceleration of the rate of rise (Houston and Dean 2011) has been detected. Examples of papers that projected sea level increases lower than the range discussed in the fourth IPCC report are Bouwer (2011), Chu et al. (2010), Czymzik et al. (2010), and Xie et al. (2010).

Temperature Increases

Governement assessment reports note that US temperatures have risen 2°F since 1961. However, conclusions about the extent of temperature increase depend heavily upon the start date for the calculation. Perhaps by coincidence, a start date of 1961 gives the most alarming rise. In contrast, there is almost no rise from 1938 to 2011 in the US. The same is true for sea surface temperature changes. This is because natural climate oscillations (e.g., Wyatt et al. 2011) produced a warm period in the mid-twentieth century with a cool period in the 1960s.


Reports assert that floods are increasing, but data do not bear this out. Hirsh and Ryberg (2011) showed that there is no trend toward increasing flood magnitudes in any region of the US, and a small decrease in the Southwest. Arrigoni et al. (2010) showed that climate change in the northern Rocky Mountains over 59 years has not significantly affected basin flows, although human habitat modifications have reduced the difference between minimum and maximum flows. Kundezewicz et al. (2005), in a global analysis of 195 long series of daily flow records, rejected the hypothesis of a growth in maximum daily flows. Increasing trends in flood damage can be fully accounted for by rising population and wealth.

Regional Drought Frequency

According to assessment reports, regional droughts are increasing in frequency and severity. However, they typically do not support this contention with any reliable data. Droughts are difficult to characterize and methods for doing so have become more sophisticated over time. The actual quantification of the “area” of a drought is also extremely subjective and no standard methods exist, nor do long-term standardized data.

Data related to precipitation and drought activity do not appear to support the contention of increasing drought frequency and severity and suggest that drought patterns are complex. For example, there has been a 5% increase in overall precipitation in the US rather than increasing drought. Sheffield et al. (2009) found that large-scale droughts follow ENSO and northern Pacific and Atlantic SSTs. This relation to ENSO activity is confirmed in a study in the US Southwest (McCabe et al. 2010). Globally, the mid 1950s had the highest drought activity and the mid 1970s to mid 1980s had the lowest, rather than a simple increasing trend. Again, picking the mid-1970s as a start date will give a false appearance of an increasing trend.

Extreme Storm Events

Assessment reports allege that extreme storm events are increasing even though storm severity per se is not reported or documented in any government archives. A “storm” is not even a well-defined object in climatology. There is an apparent increase in the number of tornados over time. However, improvements in radar quality and coverage over the past decades cause a detection bias trend, with more, smaller tornados being detected and recorded over time. Furthermore, increases in available disaster assistance aid have encouraged more frequent reporting of smaller storms in efforts to get disaster aid. Counting only category F4 and F5 events, which are relatively consistently detectable and recorded, there is no trend over the past 100 years (Balling and Cerveny 2003).


Hurricane strength is said to be increasing. This can likely be attributed to increasing satellite coverage and resolution, which tends over time to more accurately capture the hours when a storm is at maximum strength. A study that corrects for storm detection ability over time (Vecchi and Knutson 2011) finds no trend in Atlantic hurricanes over the period of 1878 to 2008. Studies of landfall hurricanes (Balling and Cerveny 2003) also show no trend. The last cat 3+ landfall hurricanes to hit (i.e., with the hurricane eye) the continental US were in 2005


Reports suggest that warmer temperatures and changing precipitation patterns will cause more fires and affect the seasonality of fires. Indians and early European settlers both used fire extensively. Areas converted to agriculture (e.g., the Great Plains) now see almost no fire. Some western forests have higher fuel loads than 200 years ago. In the context of these and other large landscape changes, no one has documented a change in fire regimes in the US that can be attributed to climate change. In fact, the largest historical fires were in the West around 100 years ago. Human activities (changes in fuel loads, increased ignition sources, arson) have on the other hand been clearly documented effects on fire extent, as have “let burn” policies in the West, which have only been implemented in the past few decades..

Algal Blooms

Reports indicate that harmful algal blooms in aquatic ecosystems have become more frequent, intense, and widespread. Climate change is only one factor potentially causing harmful algal blooms, with increasing nutrient runoff a clearly important factor. There is no basis for ascribing trends in blooms to climate change. There is also an increasing ability to detect them as satellite imagery improves over time.

Changes in Ecosystems

There are studies showing responses to biota that are “consistent with” warming, but most of these are actually positive, whereas negative effects are hypothetical (e.g., phenology “might” be disrupted). For example, changes in bird migration and nesting dates indicate adaptation to changes rather than an alarming situation. The clearest data pertain to long-term trends in plant growth. These studies, with a few local exceptions, show regional to global net primary productivity (NPP) to have been increasing in the past 50 to 100 years (Alcaraz-Segura et al. 2010; Bellassen et al. 2011; Jia et al. 2009; Kohler et al. 2010; Lin et al. 2010; Nemani et al. 2003; Tian et al. 2010) due to both rising CO2 levels and increasing temperatures. If warming since the Little Ice Age is leading to increased NPP, this is difficult to construe as problematic.


Within the United States, the claim that bad climate effects can “already” be detected is a totally subjective and unsupported hypothetical.

Literature Cited

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Alcaraz-Segura, D., Chuvieco, E., Epstein, H.E., Kasischke, E.S., and Trishchenko, A. 2010. Debating the greening vs. browning of the North American boreal forest: differences between the satellite datasets. Global Change Biology 16:760 770.

Anagnostopoulos, G.G., Koutsoyiannis, D., Christofides, A., Efstradiadis, A., and Mamassis, N. 2010. A comparison of local and aggregated climate model outputs with observed data. Hydrological Sciences Journal 55:1094 1110.

Arrigoni, A.S., Greenwood, M.C., and Moore, J.N. 2010. Relative impact of anthropogenic modifications versus climate change on the natural flow regimes of rivers in the northern Rocky Mountains, United States. Water Resources Research 46:W12542; doi:10.1029/2010WRO09162.

Balling, R.C., and Cerveny, R.S. 2003. Compilation and discussion of trends in severe storms in the United States: Popular perception v. climate reality. Natural Hazards 29(2):103 112.

Bellassen, V., Viovy, N., Luyssaert, S., LeMarie, G., Schelhaas, M.-J., and Ciais, P. 2011. Reconstruction and attribution of the carbon sink of European forests between 1950 and 2000. Global Change Biology 17:3274 3292.

Bouwer, L.M. 2011. Have disaster losses increased due to anthropogenic climate change? Bulletin of the American Meteorological Society 92:39 46.

Chu, P.-S., Chen, Y.R., and Schroeder, T.A. 2010. Changes in precipitation extremes in the Hawaiian islands in a warming climate. Journal of Climate 23:4881 4900.

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Hirsch, R.M., and Ryberg, K.R. 2011. Has the magnitude of floods across the USA changed with global CO2 levels? Hydrological Sciences Journal doi:10.1080/02626667.2011.621895.

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Kundzewicz, Z.W., Graczyk, D., Maurer, T., Pinskwar, I., Radziejewski, M., Svensson, C., and Szwed, M. 2005. Trend detection in river flow series: 1. Annual maximum flow. Hydrological Sciences Journal 50(5):797 810.

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Loehle, C. 2003. Competitive displacement of trees in response to climate change or introduction of exotics. Environmental Management 32:106 115.

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Nemani, R.R., Keeling, C.D., Hashimoto, H., Jolly, W.M., Piper, S.C., Tucker, C.J., Myneni, R.B., and Running, S.W. 2003. Climate-driven increases in global terrestrial net primary production from 1982 to 1999. Science 300:1560 1563.

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please fix
more acidic is a pH decrease not increase


One government draft report indicated that ocean pH has increased (become more acid) by 0.1 units
became less base.


Craig – just a quick correction, pH has allegedly decreased (become more acid), not increased.

Ian H

Surely pH would need to DECREASE for the seas to become more acidic.

John Marshall

So we have severe drought increasing and increasing flooding.
This paper looks like a direct reprint of the latest IPCC forecasts.

Peter Plail

May the scales fall from the eyes of the alarmists, that they recognise the truth.
Sadly for them, the opportunity for staking their claims as saviours of the planet from deadly CO2 are vanishing.


“The last landfall hurricane to hit (i.e., with the hurricane eye) the continental US was Katrina in 2005.”
I don’t disagree with anything you have said in this article, but you need to be accurate. I believe you are referring to ‘major’ hurricanes, in which case your statement is true. Otherwise, what about Dolly, Gustav and Ike that all made landfall as Cat 2 hurricanes in 2008 ?

ian middleton

If my chemistry serves me correctly an increase in pH makes something more alkaline. Or has AGW changed the rules.


A welcome post.
Great clarity and a much needed antidote to hysteria.


Re: tornados and algal blooms–Here in central Fla. when I was a 1950’s teenager we didn’t have the faintest idea we had tornados because there were only 1/4 the current population and nothing like our current detection and reporting capability. Algal blooms have now ruined many formerly pristinely clear lakes but this well know to be caused by the mountains of fertilizer used on lawns and in agriculture.

John West

“These studies, with a few local exceptions, show regional to global net primary productivity (NPP) to have been increasing in the past 50 to 100 years (Alcaraz-Segura et al. 2010; Bellassen et al. 2011; Jia et al. 2009; Kohler et al. 2010; Lin et al. 2010; Nemani et al. 2003; Tian et al. 2010) due to both rising CO2 levels and increasing temperatures.”
That seems all well and good with oxygen @ 20.8%, but wait until the plants have knocked that down to less than 19.5% and see how you like it then. …….. (/sarc)


> ocean pH has increased (become more acid) by 0.1 units, …..
Should be “…pH has decreased…” if the ocean became more acidic.

Steve Keohane

Thanks Dr. Loehle, great summation of a nonevent. I am still puzzled how you and others can put together temperature proxies that are consistent with human observation, as well as being consistent with what I read since the 50s, and the first IPCC report. Then the whole field of climate is absconded by a dire fantasy. I appreciate your well-grounded perspective.

I’m sure the usual parade of disagreement will rise to the occasion? The whole point of alarmist rhetoric is to…..raise alarm. Not to use data, or the logical conclusions to be drawn from data, but to point out ‘impacts’ that ‘could be’ due to the CC Bogeyman. One mustn’t let reasoned conclusions based on observable facts get in the way; and if they do, quickly discredit the offering author. So, Dr. Loehle; prepare thyself for the usual litany of half-truths! Trolls, do your best!

Within the United States, the claim that bad climate effects can “already” be detected is a totally subjective and unsupported hypothetical [fill in the missing word(s) please].

mike about town

good stuff….thanks!


Nice summary. However, Irene made landfall in NC in 2011. I think you might have meant ‘major hurricane’, cat3+.

richard verney

I do not live in the USA but do consider that it should be used as a benchmark for assessing the cAGW claims because it is a large land mass and the ‘quality’ and extent of available data is high in relative terms when compared to the global position.
Given that there has been little if any warming since the mid 1930s in the USA, one can see no reason why the USA should be exhibiting any adverse signs of climate change.

“Climate Change Impacts In The USA is Are Already [NOT] Happening”
Subject of head is ‘Impacts’, plural.
/Mr Lynn

WRT pH, from what I understand it’s still firmly on the alkali side of the scale, and people should also realize that ‘acidic’ or relatively more acidic doesn’t mean bad, nor does alkali or relatively more alkali mean good. It’s like these people never heard of chemical burns outside of acid attacks in horror movies. They should watch The Seven Doors of Death, in the begining they melt a warlock with lye.

Note sent to Anthony about PH typo.
ImranCan: yes, I’m only counting >Cat 2 hurricanes
Murry Grainger: hypothetical is the last word in the sentence. Not a hypothetical something.


I cannot see why there should be more extreme wheather events.
Electric energy is produced using a potential e.g. a difference in height from power house to water reservoir. Gravity accelerates water downwards the water pipe which then drives the turbines.
What would happen when one could rise the whole location updwards?
Nothing. Only the elevation difference between water reservoir and turbine counts, not the elevation of the whole system.
Same with wheather. If you’ld increase the global mean temperature you won’t increase the differences in atmospheric pressures. Although there is more moisture in the air to be expected at an increased mean temperature, the engine driving wind and wheather doesn’t get stronger.
Energy as such can’t do any work. What one needs is a potential. To heat earth up doesn’t raise any potential. To the contrary. Melting the polar ice caps will decrease the useable potential for wind and storms.
Speaking of hurricans there is another potential in charge, I believe. One needs shearing winds to create a vortex and an up/down potential that is the difference between sea surface temperature and the temperature of the upper troposphere.
So how will heating up the blue marble as a whole increase that potential?


Most people are scientifically and mathematically illiterate and thus have not a clue what pH represents and thus can be fooled by the dubious and intentional use of the 30% more acidic claim. A change of pH of 0.1 units does in fact represent a 26% change in the hydrogen ion (H+ or H3O+) concentration.

Nice resource Craig. Bookmarked, under Loehle.

Owen in GA

This reminds me of the scene in “The Princess Bride” between Wesley and Vizzini – “What you do not smell is Iocaine powder…”
I always love observing the null set, it is quite comforting at times.


I can’t help it but in my opinion effects of climate change are already very observable – taxes went up, prices went up, people are more stressed, live in worse conditions, more people are unemployed and poor – all of it because of climate change…


The need for accuracy is important. You should change it to read “no major (cat 3+) hurricanes since Katrina”. You would be hard pressed to find anyone living around Galveston Bay who thought Ike was a minor storm.

corporate message

Their reasoning behind the “acidity” increase dealy, is that what they are talking about is no longer about pH, you see. It’s something different they are measuring related to free ions, I assume.

Craig says:
One government draft report indicated that ocean pH has increased (become more acid) by 0.1 units
the pH =-log [H+]
we have a pH scale of 0-14
pH=0 is 1 mole H+ per liter
7.00 is completely neutral water.
14 is where the pOH is 0, i.e 1 mole per liter OH-
So if they say that the pH increased by 0.1, it means the water became a bit more alkaline, not acidic.
An increase in pH, i.e. water getting more alkaline is better for life in general.
Seeing that the actual cause of the warming is natural, i.e. more sunshine and or less clouds and or/less ozone shielding, etc.
it actually makes sense for me to disregard reports that the oceans have become more acidic due to CO2 emissions.
Namely, with clearly more (natural) heat ending up in the SH oceans, we would expect to find that, similar to boiling your tap water (to remove CO2), you get
heat + HCO3- => CO2 + OH-
which raises the pH
which makes the water more alkaline.
So, I have to correct you. If they say the pH is raised by 0.1 then it has become more alkaline.
Not more acidic.

Yep, another typo: Climate Change Impacts Are … not “is”
I’m trying to set a record.

David S

Dr Loehle
Can you please clarify whether you think Ike was a hurricane when it made landfall in September 2008? My understanding is that it was a Cat 2 at landfall and still a Cat 1 about 100 miles inland, meaning that the eye would have been well over the coast before it was downgraded to a triopical storm. Your general argument is still valid, but I think Chris Landsea’s various papers and presentations make the point better, particularly when one looks at the ACE index numbers or the hurricane damage figures normalised for population growth and intensity.

FYI: A change of -0.1 in pH results in a change in concentration of H+ (or H3O) ions by a factor 10^0.1, which equals 1.26. Perhaps rounding this number to 1.3 is where the ‘30%’ comment came from? Not a big effect in the scheme of things…

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When it comes to water measurements, and understanding, sometimes the best place to get info, is on hobbyist sites such as reef central.
There is a bit of difficulty relating all the terms; .General Hardness or GH, German Degrees hardness, kH, acidity, basicity, alkalinity and so on. It’s not clear cut understanding across the board.

David A

Good post Craig. I have always noted that the claimed harms of CAGW are missing. The benefits are KNOWN, the harms are THEORY, unsupported by observations. Usually the alarmist type run away from a post like this.

Bob Moss

Hurricane Rita (cat 5, cat 3 at landfall) was after Katrina by a few weeks but, of course, does not change the point that it has been several years since a major hurricane hit the USA.


Are any of those changes out of the ordinary in any way?

Regarding the ocean pH value, log 1.3 = 0.114 where the log is to base 10.
OR 10^-7.9 / 10^-8 = 10^0.1 = 1.26
This seems to suggest that a reduction in pH value of 0.1 and an increase in H ions of 30% in sea water do seem to roughly correspond.
I suspect that this figure derives from the claim, based on ice core analysis, that atmospheric CO2 has increased by about 30% since the start of the industrial revolution. It is then assumed that dissolved CO2 in the oceans must also have increased by 30%, hence the 0.1 change in pH. This seems plausible if the ice cores can be believed. But my view is that the criticisms of ice core analysis by Jaworowski, together with the historical direct measurements of atmospheric CO2 collated by Beck and the several analyses of stomata records call into question the officially accepted history of atmospheric CO2 levels. Thus, it is quite possible there has been no trend in the pH value of sea water at all.
Just hypothesizing !

Dodgy Geezer

I would like to share with you the results of a simple google on ‘aquarium ph levels’ – here is an excerpt from the nearest aquarium advice site:
“…Unless you intend to breed a species that is very particular about water chemistry, you will find that the stability of the pH in an aquarium is far more important than the exact value. Large, rapid changes in pH are often fatal to fish. Any change greater than 0.2 in a 24-hour period will cause physical stress for most fish.
Most fish will do fine in a broad range of values starting as low as 6.5 and going up to 8.0. Some species will do better at even higher or lower values than these, but for all practical purposes, it is best to allow the pH to settle at a value and simply leave it there. As a natural part of the biological processes in an aquatic environment, the pH in the tank will become increasingly acidic over time. The change is very gradual, though, and so poses no real threat to the fish…”

So if I’m a warmist, I can alter the pH value in my test tank by .04 in 10 minutes, and document definite physical stress. But if I’m a ‘denier’, I can swing the pH from 8 to 6.5 over a few months and demonstrate no impact at all.
Isn’t climate science wonderful…..?

A change (decrease) of 0.1 on a 14 point PH scale is not 30% no matter how you twist it. It is possible that warming water could lose net CO2 and become more alkaline absent rising atmospheric levels as HenryP noted, but I can’t assess the net effect myself with both processes going on.
On hurricanes, a storm “hitting” the coast means the eye hit, and cat 2 isn’t much of a storm so I discounted those.


“Because pH is a log scale, estimating percent increases in acidity is problematic and a change of 0.1 units could not represent a 30% change in acidity as stated.”
I was about to make the same observation about this statement’s accuracy as MikeL did, i.e., that it’s not really off by too much. But my conclusion is different. Dr. Loehle’s argument would be more bulletproof if he avoided reliance on such debatable points.

Hu McCulloch

Craig — pH is on a log 10 scale, not a natural log scale. So a decrease (not increase) of .1 units increases H3O by a factor of 10^.1 = 1.26, or about 30%.
According to two recent survey articles by Dana Royer, over the last 550 million (not thousand) years, CO2 has mostly been in the range 1000-3000 ppm. Despite this “acid” environment, the seas did just fine, and laid down all the limestone we see around us, so I’m not too worried that the clams are going to have to swim around naked. . The seas are a huge buffering mechanism and can absorb a lot of CO2 without much change in pH.


Craig – suggest you fix the text on hurricanes to be accurate. As Bob Moss also points out, Rita was after Katrina and a Cat3 hurricane. These kind of errors don’t affect the overall storyline – which is great – but they cause an erosion of credibility, and its easy to start wondering “well … if he can’t even get that right …..”

A lot of other hurricanes have hit outside of Katrina. Ike, Irene, Gustav…

“…The last landfall hurricane to hit (i.e., with the hurricane eye) the continental US was Katrina in 2005…”
Weren’t there a couple AFTER Katrina in 2005?
IIRC, Rita and Wilma were both 5’s.
Gustav and Ike in 2008 only made it to cat 2’s at landfall, but still hit the mainland.
I think Ike of 2008 would be the last “landfalling” hurricane.

Hu McCulloch

RE unprecedented floods —
There’s a new art movie out titled The Great Flood. From the blurb:

The Great Flood of 1927 [was] a natural catastrophe that sparked a transformation of American society and music. In the spring of 1927, the Mississippi broke out of its earthen embankments in 145 places and inundated 27,000 square miles. The disaster became a major force in spurring the Great Migration of rural sharecroppers to northern industrial cities, triggering the evolutioin of acoustic country blues into urban electric blues, then R&B, rock, and jazz.

Must have been the CO2! 😉


corporate message says:
March 8, 2012 at 6:39 am
When it comes to water measurements, and understanding, sometimes the best place to get info, is on hobbyist sites such as reef central.
and even they don’t get it right……
But aquariums in the house are a decent example of why the ocean acidification does not work….
It’s common for CO2 levels in a closed house to be 1000 ppm or higher. Aquarists maintain pH by simply adding buffer….
The oceans will not become more acidic unless they run out of buffer….and as long as carbon dioxide is converted to calcium carbonate that won’t happen

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Boiling tapwater removes some dissolved gases due to the pipe water pressure – but also removes carbonates of calcium and perhaps magnesium ….so you see a lime scale on the kettle – hardness vs acidity – chemists !

Jimmy Haigh.

Good post. Take the bones out of that, Warm-mongers.

Julienne Stroeve

Dr. Loehle, would you care to comment on a recent paper in Science about ocean acidification that examines the geologic record for context relating to ocean acidification. The research group (twenty-one scientists from nearly as many different universities) reviewed the evidence from past known or suspected intervals of ocean acidification. The work provides perspective on the current trend as well as the potential consequences. They find that the current rate of ocean acidification puts us on a track that, if continued, would likely be unprecedented in last 300 million years.
Citation: “The Geological Record of Ocean Acidification.” By Bärbel Hönisch et al. Science, Vol. 335, No. 6072, Pg. 1058-1063. March 2, 2012. DOI: 10.1126/science.1208277.