This statement is at odds with comparisons between the warming we have observed and the warming predicted by climate models. These comparisons show good agreement and do not support the claim that warming is far slower than predicted. That the authors of this statement do not know about these published model-data comparisons has led them to make these false statements.

For example of the agreement between observed and predicted warming, see Fig. 4b of Cowtan et al. (2015, Geophysical Research Letters, https://doi.org/10.1002/2015GL064888)

This statement is based on selective misuse of evidence. There are benefits of CO2 for vegetation growth (though these benefits are often overstated) but these benefits will likely be limited by nutrient shortage and they may be overcome by changes in climate (e.g. increased drought) caused by the same increases in CO2.

For example, IPCC AR5 WGI Chapter 6 reported that "It is very likely... that nutrient shortage will limit the effect of rising atmospheric CO2 on future land carbon sinks". https://www.ipcc.ch/report/ar5/wg1/

This is only true for a narrow definition of a pollutant. If a pollutant is something that causes adverse effects on natural and human systems, then CO2 is a pollutant when it is increased rapidly in the Earth's atmosphere and increases the risks of damaging effects.

See here for an explanation: https://rationalwiki.org/wiki/CO2_is_Green

This statement is wrong: climate models do include the carbon cycle too (they are then called Earth system models) and these include the effects of increased atmospheric CO2 on vegetation. That the authors of this report do not even know that these effects are included in climate models illustrates how little they really know about climate science.

For evidence that CO2 influences are indeed included in IPCC science and projections see e.g. Box 6.4 ("many models now have an interactive carbon cycle") and Box 6.3 ("The Carbon Dioxide Fertilisation Effect... Elevated atmospheric CO2 concentrations lead to higher leaf photosynthesis and reduced canopy transpiration, which in turn lead to increased plant water use efficiency and reduced fluxes of surface latent heat. The increase in leaf photosynthesis with rising CO2, the so-called CO2 fertilisation effect, plays a dominant role in terrestrial biogeochemical models...") of IPCC AR5 WGI https://www.ipcc.ch/report/ar5/wg1/

The current period of warming is not because the Little Ice Age ended by 1850. Climate scientists study the causes of warming and cooling period and calculate their effects on our climate. These studies show that natural warming after the Little Ice Age was complete by the late 1800s. The warming from the late 1800s to the present is all due to human-caused climate change, because natural factors have changed little since then and even would have caused a slight cooling over the last 70 years rather than the warming we have observed.

See Figures 3b and 6c of Tett et al. (2007, https://doi.org/10.1007/s00382-006-0165-1) for example.

No support is provided for this statement, which isn't surprising since he probably just made it up to suit his narrative.

There's a whole lot of baloney in the previous sentence.

Untrue. There has been clear warming of the air temperature over land, of the ground temperature, of the sea surface temperature, of the sub-surface ocean temperature, and warming of the troposphere too. See IPCC AR5 SPM part B.

This statement is misdirecting the readers/viewers. There is a strong consensus about the key elements of global warming and climate change, but this hasn't been achieved by scientists voting but by analysing the "facts" (i.e. the evidence for whether the climate is changing -- it is [IPCC AR5 SPM part B] -- and the evidence for which factors could have caused the observed changes -- for the global-scale warming and many associated changes, there is firm evidence that human drivers are dominant in recent decades [IPCC AR5 SPM part D]).

IPCC, 2013: Summary for Policymakers. In: Climate Change 2013: The Physical Science Basis. Contribution of Working Group I to the Fifth Assessment Report of the Intergovernmental Panel on Climate Change [Stocker et al., eds.]. Cambridge University Press, Cambridge, United Kingdom and New York, NY, USA. Available here: http://www.ipcc.ch/report/ar5/wg1/

"collapse" is commonly taken to mean "fail suddenly and completely", but in the context of ice sheets the scientific use of "collapse" can encompass much longer timescales (even multiple centuries) and it would be informative to make this clear. For example, IPCC AR5 WGI (Chapter 13 on sea level change) use it this way:

Future climate forcing could trigger such an unstable collapse, which may then continue independently of climate. This potential collapse might unfold over centuries for individual bedrock troughs in West Antarctica and sectors of East Antarctica.

Without this clarification, "collapse" may be misinterpreted to mean something happening over timescales of a single decade or much shorter timescales -- especially when combined with earlier language about refugees "fleeing inland" due to a "rapid disintegration".

There is strong evidence that solar forcing cannot explain much of the observed warming at all. The "fingerprint" of solar forcing do not match the observed changes at all, neither over time nor space. Solar forcing would warm both the stratosphere and the surface of the Earth, whereas CO2 warms the surface (and the troposphere) but cools the stratosphere. Using radiosondes and (more recently) satellites, we observed a warming surface and troposphere together with a cooling stratosphere. See Santer et al. (2013) for one of many studies providing this evidence:

Benjamin D. Santer, Jeffrey F. Painter, Céline Bonfils, Carl A. Mears, Susan Solomon, Tom M. L. Wigley, Peter J. Gleckler, Gavin A. Schmidt, Charles Doutriaux, Nathan P. Gillett, Karl E. Taylor, Peter W. Thorne, and Frank J. Wentz Human and natural influences on the changing thermal structure of the atmosphere PNAS 2013 110 (43) 17235-17240, doi:10.1073/pnas.1305332110

This is incorrect. There is a range of published evidence that future warming of 2 degC would have a net adverse effect. In terms of ecological responses, for example, Warren et al. (2013) assess the changing climate ranges of almost 50,000 animal and plant species and find that projected climate changes would greatly reduce these climate ranges. From the abstract:

Our global analysis of future climatic range change of common and widespread species shows that without mitigation, 57±6% of plants and 34±7% of animals are likely to lose ≥50% of their present climatic range by the 2080s.

Warren R, VanDerWal J, Price J, Welbergen JA, Atkinson I, Ramirez-Villegas J, Osborn TJ, Jarvis A, Shoo LP, Williams SE and Lowe J (2013) Quantifying the benefit of early climate change mitigation in avoiding biodiversity loss. Nature Climate Change 3, 678-682 (doi:10.1038/nclimate1887).

This statement is incorrect: there are multiple examples where we have predicted the behaviour of climate, ranging from the seasonal cycle, the response to volcanic forcing, the warming of recent decades to some palaeoclimatic changes. See: Schmidt, G.A. & Sherwood, S. Euro Jnl Phil Sci (2015) 5: 149. doi:10.1007/s13194-014-0102-9

It is unfortunate that John Christy dramatically overstates the implications of his comparison between model simulations and tropical tropospheric temperatures to imply that we can make no predictions, because this is an important challenge for testing climate models from which we can learn much about climate response and about how to evaluate confidence in models. But his demonstration has flaws in its presentation (e.g. using too short a baseline period) and distracts from the key information about how models and observational trends differ in this region. See Santer et al. (2017) for a comparison and an assessment of the implications -- there are diffeences in simulated and observed warming trends in this part of the atmosphere but they are much less than Christy claims and don't support a blanket assertion that "we cannot predict" climate.

Judith Curry's interpretation of the IPCC's assesment as meaning a range from 51 to 99 percent is incorrect. First, the range extends beyond 99 percent, because natural influences may have offset some of the warming from human activity. Second, because it suggests a uniform likelihood within that interval whereas the likelihood that the real contribution is near the edges of the range (i.e as low as 51 percent of the observed warming or as much as one and a half times the observed warming).

There is indeed a great deal of uncertainty, but the IPCC assessed range takes this into account -- by quantifying those uncertainties than can be quanitified, and by making a broader, more conservative range to account for those that can't be quantified.

Assessments of the cause of recent warming consistently find that human activity is the dominant cause of recent warming. These assessments have considered other causes such a natural forcings and climate dynamics that cause internal variability. While our knowledge of these is incomplete, there is enough agreement between models and observations to discount, with high confidence, a contribution from internal variability that explains more than half the observed warming.

The statistical models used in this report co-authored by Christy are flawed and thus do not support his statement that Mother Nature can cause the observed warming trends on her own. They suggest that these trends arise from cumulative anomalies of ENSO or cumulative anomalies of solar irradiance, but offer no compelling physical basis for this hypothesis. There is no consideration that a warmer climate would cause increased loss of radiative energy to space, nor that a cooler climate would decrease the emissions of radiation to sapce. This effect is necessary to explain how the Earth's climate has remained within a relatively small range of mean temperatures for much of the Earth's geological history, yet their hypothesis assumes that a step up in temperature (due, e.g. to an El Nino event) would be sustained even after the El Nino had dissipated, because they use the cumulative ENSO index. Furthermore, a cumulative variable must have a physically-defined baseline from which the anomalies are defined, which has not been done in this case. Otherwise, the baseline can be changed to produce an entirely arbirtrary upward or downward trend in the cumulative variable, and thus support a false claim that the cumulative variable can "cause" a trend in the climate.

Need to be careful to distinguish between whether a study shows that the likelihood of an extreme event has changed, or whether it predicts that the likelihood has changed.

Yes, the pattern of observed warming matches the pattern projected in 1989 well. But note that this is a qualitative comparison and also that a good match in the pattern of warming does not confirm that the amount of overall warming was simulated correctly (which is difficult to evaluate from that study because the forcings applied to the model differ from the real-world history of forcings). The pattern of warming arises from the various feedback processes that cause high northern latitudes to warm more than other latitudes, especially in winter, and for land to warm more than the oceans (associated with humidity and cloud responses as well as greater heat capacity of the oceans than of the land) and the qualitative agreement between model-simulated and observed warming provides evidence that the climate model is representing these processes in a reasonably realistic manner.

There is supporting evidence for this claim (summarised in chapter 10 of IPCC WGI AR5: http://www.ipcc.ch/report/ar5/wg1/). Taking into account uncertainties in the internal variability, in the strength of human and natural forcings and in the strength of the climate model simulations of the temperature response to these forcings, the best estimate is that all of the observed warming since 1950 is due to human influences. Because of the uncertainties, the human contribution could be larger or smaller than this, but it is "extremely unlikely" (defined by IPCC as less than 5% chance) that it is as low as only half the observed warming.

Early 20th century warming is an interesting issue and potential explanations include a role for greehouse gas warming along with natural influences (internal and external variations). There is little mid-century cooling, but there is mid-century period of little change and there are consistent explanations of this involving offsetting influences of greenhouse gas warming and sulphate aerosol cooling.

This statement implies that we know the magnitude and phasing of large-scale ocean oscillations in the real world, and that there is strong evidence that climate models are unable to simulate such behaviour. Neither is correct. Furthermore, there is no clear evidence that ocean oscillations have a significant affect on global warming on century timescales.

This is incorrect: assessments of the cause of recent warming consistently find that greenhouse gases are the dominant cause of recent warming. These assessments consider other climate forcings, including natural effects (the most important ones on timescales of decades are variations in solar and volcanic activity) and human-caused aerosols, but the most likely effect of these other forcing would have been to cause global cooling in recent decades. Thus, there is agreement between scientists that the observed warming is due to human-caused emissions of greenhouse gases.

Yes, this is correct. The overall picture is obtained by the regular assessment of the whole body of these (many) thousands of scientific studies, by bodies such as the IPCC.

Yes, this is supported by the observations.

"surging" suggests that the faster sea level rise in 2016 has continued, whereas the surge was between Nov 2014 and Feb 2016, as indicated in WMO's statement and in the data.

This statement is overly confident and not based on a broad consensus in the literature. Even the cited study states "we cannot be certain that the current year is warmer than any single year earlier in the Holocene due to centennial smoothing of the Holocene stack and original resolution of the underlying proxy records". The most recent IPCC assessment indicates only moderate confidence that 1983-2012 was the warmest 30-year period in the last 1400 years and limited this to the Northern Hemisphere rather than the global average.

This is a diversionary tactic: the concern about CO2 is not about its smell, its colour or its direct toxicity; instead it is about its effect on the Earth's climate. So it is a strawman statement that may be easily demolished but not relevant to the concern about CO2 and climate change.

Projections of future warming can't be made from observations alone: we need understanding of the mechanisms and physical processes. Neither of these are provided by the quoted website, which instead contains inaccurate articles about supposed adjustments to temperature data and claiming a new 'little ice age' is already here -- both of which have been shown to be incorrect by scientific research (for example section 1.3.2 of IPCC AR4 WGI compared global temperature records from various vintages and found broad consistency).

The impression given by this statement is that CO2 fertilisation of vegetation growth outweighs all the adverse impacts of climate change. Joy or concern should be based upon an assessment of all the impacts and not just on one aspect, as done here. Comprehensive assessments (e.g. IPCC WG2) consistently find climate change to be a cause for much concern, not for "much joy", as claimed by the author.

The title is inaccurate. The IPCC, for example, a leading and authoritative source of climate change information, includes benefits as well as adverse effects in its assessment. Even the second sentence of its WG2 Summary for Policymakers (SPM) notes that there are potential benefits, and some of these are covered in the remainder fo the SPM. While the author may feel that the balance isn't right, it is inaccurate to say that the potential benefits are never stated.