Weather

Weather is king in the sense that it is what impacts us every day and adds up over time into climate. Our weather in Virginia depends a lot on storms cooked up in the Pacific and the 500 MB flow across the country. If it is E/W (zonal), then we will see less extreme weather in general. More N/S (blocked) can give more extremes of warm and cold and more storminess (again in general). The nature of the flow (zonal or blocking) is determined by broader scale weather patterns as measured by indexes like North Atlantic Oscillation (NAO) and the Artic Oscillation (AO) and others but those two are the most relevant for us. As can be seen both in the forecasts below and the in running means in the "Climate" section, NAO and AO can change on a weekly or monthly basis but also exhibit long term patterns that can last for a decade.

The storms in the pacific that are so important to our weather depend on broader forms of weather such as El Nino Southern Oscillation (ENSO). The ENSO index shown below is multivariate which is a measurement of ENSO effects beyond the sea surface temperature in a particular area of the Pacific ocean. Generally a positive ENSO index (red) is going to give us juicier storms in the southern jet stream, usually in winter and often as rain. Negative ENSO has northern jet stream systems that will often go north and west leaving us drier. A lot depends on AO and NAO (which again are only indexes of weather effects, not causes of weather).


current 500 MB flow
surface pressure
3 hr change in pressure

surface temperature
surface winds

Weather Forecasts

The 500 MB foreast plots are shown below. These come from weather models.

Below are the AO and NAO forecasts which also use weather models.

Below is the ENSO forecast (SST only, it is harder to predict the multivariate effects). That is the closest thing on this page to a climate model output although the model uses initial conditions from current weather and ocean measurements and has finer granularity. Like all climate models, the ENSO prediction is often inaccurate due to incorrect model parameters and the chaotic influences on weather.

Climate

Years of weather get averaged into climate. That means that the vagaries of weather are added up and become climate. As a chaotic process, the ripples and vortexes in the jet streams shown at 500MB above and many other fluctuations will tend to average out over time. The broader area indexes like NAO, AO, ENSO shown below are simply the measurements of certain types of weather shown over many years. They exhibit cycles of behavior over decades that are indications of longer cycles. For example, through much of the 1990's the AO index had been relatively high except for a distinct dip after the eruption of Pinatubo.

The AO and NAO above are atmospheric indexes reflecting the nature of the ripples in the jet stream. A higher NAO (in red below) means a more zonal, less blocking pattern for us whih means systems will keep moving be they warm, cold, high pressure or low. Negative NAO (in blue below) means that the atmosphere is blocked which can mean moreeast coast storms under some conditions, arctic outbreaks in winter and other effects.

A higher AO (in red below) means that the circumpolar arctic jet stream is faster and there is less air movement to and from the Arctic. A lower or negative AO (in blue) means that there is a weaker circumpolar jet and arctic air can spill down towards us while very mild air can drawn up into far northeast Canada or other arctic locations.

ENSO, shown below, is a measurement of ocean and atmosphere oscillating in tandem, often with a direct effect on weather including ours. The distinction from AO and NAO is that those measure weather effects and ENSO can cause weather (although it is also a measurement of effects)

Global Warming Facts

Global Warming is ongoing
The earth is warming about 0.13 degrees per decade over the period of 1979 to present using the satellite data. The 2000's warming is less than the 1990's warming.

click for details


CO2 is rising and the rise is mostly man made
The annual rise in atmospheric CO2 is measured to be about 1/2 of the annual man made CO2 (estimated from fossil fuel usage and cement manufacturing)

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Increased CO2 causes warming
Simple models show that the increase in CO2 causes an increase in absorbed radiation, part of which is emitted back towards the earth

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However, natural temperature fluctuations are huge
The "global average temperature" can rise or fall 0.03 in a day which is at least 2 years worth of "global warming"

click here for raw data
or click on graph to the right for graphical data (use 14,000 feet chan 05)


(note: seasonal rise and fall is due to NH land heating in the summer)
Likewise, Arctic fluctuations are much larger than the secular rise from "Arctic Amplification"
The temperature of the Arctic can rise or fall 10C in a week which is about double the "Arctic warming" so far

click for Arctic temp page

Global Warming Model Failures

Models Failed to Predict Negative AO
There were climate science papers written in the late 90's that that claimed that the increase in the AO index in the 80's and 90's (refer to graph above) was caused by AGW as predicted by models. Since that time, AO has fluctuated and is currently quite negative. That negativity has now been blamed on lack of Arctic sea ice (a quite speculative theory). If that is true, why didn't the models predict decreasing AO back in the 1990's?
Global Warming has Stopped Accelerating
During the early 2000's there were a flurry of papers with the idea that global warming was accelerating, mistaking the natural temperature rise from the strong 1998 El Nino for man made warming. Some papers also speculated that El Ninos would increase in prevelance and severity. That has not happened. ENSO has reverted to a more balanced mode and global warming has decelerated. Since that time global warming has been consistently on the low side of predictions. It is likely that the predominance of El Nino in the 80's and 90's (refer to graph above) added some natural warming to the warming from CO2.

Bottom Line

There is little doubt that the ongoing increase in CO2, a well-mixed greenhouse gas, will raise global average temperatures some small amount. A feedback of increased water vapor may multiply that effect but it may not since water vapor is never well-mixed. The large amount of variation in weather indicates to me that weather is a controlling factor on global average temperature, not an additive factor.

Recent (last decade) global warming may be 0.1C per decade or less (looking at the satellite record above) or 0.2C per decade (looking at surface stations which may have urban contamination). This is controversial because 1C per century is considered by many to be benign warming and may also indicate low water vapor feedback.

The global average temperature can rise or fall 0.1 or 0.2C in a matter of weeks due to weather, so we must ask why the same amount of rise over a decade matters. The answer is that it probably does not because natural variations dominate. Quite a few climate modelers would disagree, they point out that it will not only be warmer from CO2 but also believe that there will be an increase in average water vapor from the temperature increase from CO2 itself (i.e. water vapor feedback). The main problem with that theory is that their models use parameters determined a priori to describe the weather. Thus they can't show how weather will change in a world warmed by CO2 because they can't model weather.

As one example, will the tropics expand under global warming? Will there be increased convection in those tropics (a negative feedback)? How mixed will water vapor be in the expanded tropics? Global climate models cannot answer these questions, but the real world has some answers. The tropics expand and they contract. They exhibit increased and decreased convection. Some of the changes are directly related to the temperature, as both negative and positive feedbacks to temperature. Other changes come from external factors like solar irradiation and possibly solar geomagnetic fluctuations. Still other changes are due to terrestrial factors like ocean current fluctuations such as ENSO (El Nino versus neutral / La Nina).

The bottom line is that external factors and ocean "cycles" try to force global climate into new states, but weather tends to keep climate in its existing state. Thus I do not believe that "water vapor feedback" is a primary outcome of CO2 warming. A better explanation is that there will be water vapor modulation (weather) by various internal and external factors including CO2 warming but that long term warming will be limited just as short term warming is always limited during short term fluctuations.