Posted on February 26, by curryja Comments by Javier Summary:
Posted on September 26, by curryja Comments by Ross McKitrick A number of authors, including the IPCC, have argued that climate models have systematically overstated the rate of global warming in recent decades. A recent paper by Millar et al.
The horizontal axis is correlated with time but by using cumulative CO2 instead the authors infer a policy conclusion. The line with circles along it represents the CMIP5 ensemble mean path outlined by climate models.
The vertical dashed line represents a carbon level where two thirds of the climate models say that much extra CO2 in the air translates into at least 1. The black cross shows the estimated historical cumulative total CO2 emissions and the estimated observed warming.
Notably it lies below the model line. The models show more warming than observed at lower emissions than have occurred. The vertical distance from the cross to the model line indicates that once the models have caught up with observed emissions they will have projected 0.
The gist of the article, therefore, is that because observations do not show the rapid warming shown in the models, this means there is more time to meet policy goals. Were Millar et al. They are certainly not the first to make this claim. Histograms of model trends grey bars are based on simulations of the models, and black curves are smoothed versions of the model trends.
The ranges of observed trends reflect observational uncertainty, whereas the ranges of model trends reflect forcing uncertainty, as well as differences in individual model responses to external forcings and uncertainty arising from internal climate variability.
I have updated the IPCC chart as follows. All data are centered on Prior to the longest interval without a crossing between the red and black lines was 12 years, but the current one now runs to 18 years.
This would appear to confirm the claim in Millar et al.
How does he get this result? Using the latter blend, and taking into account the fact that when Arctic ice coverage declines, some areas that had been sampled with SAT are replaced with SST, Cowtan et al.
Figure 4 in Cowtan et al. With the El Nino at the end of the record a crossing between the observations and the modified CMIP5 mean occurs. In my version using the unmodified CMIP5 data the change to a baseline would yield a graph like this: The Cowtan et al.
That creates the visual impression of greater agreement between models and observations, but bear in mind the models are brought down to the data, not the other way around.
Apples with Apples The basic logic of the Cowtan et al. The question is whether their approach, as shown in the Hausfather graph, actually reconciles models and observations.
This might be true in some places but not in the tropicsat least prior to The linked paper by Christy et al. More generally, if the blending issues proposed by Cowtan et al. But, as I will show, the discrepancies show up in other comparisons as well. In a warming world, towards the end of the sample, each location would be expected to have a less-than-null probability of a record cold event and a greater-than-null probability of a record warm event each month.
The expected pattern was found to hold in the observations and in the models, but the models showed a warm bias.
The pattern in the models had enough dispersion in CMIP3 to encompass the observed probabilities, but in CMIP5 the model pattern had a smaller spread and no overlap with observations. In other words, the models had become more like each other but less like the observed data.
The data are centered on A good way to assess the discrepancy is to test for common deterministic trends using the HAC-robust Vogelsang-Franses test see explanation here.Latest environmental news, features and updates. Pictures, video and more. Introduction. What exactly is global warming and why is it worthy of consideration?
Global warming is the scientific phenomenon linking an increase of the average earth temperature because of a trapping of radiation within the earth like a greenhouse. I. Thesis structure Title Page Title (including subtitle), author, institution, department, date of delivery, research mentor(s) and advisor, their instututions and email adresses.
“The Great Global Warming Swindle” (DVD/video/movie) is a pseudo-documentary in which British television producer Martin Durkin has fraudulently misrepresented both the data involved and scientists who have researched global climate.
Figure 4 and 5. Two Cheers for the Greenhouse Effect. Some global warming is necessary in order to make the Earth habitable for creatures like us. The Purdue University Online Writing Lab serves writers from around the world and the Purdue University Writing Lab helps writers on Purdue's campus.