Luci e ombre

[steph]

Luci: evidenze dell'AGW.
Ombre: lacune e auspici nella modellizzazione futura del fenomeno.

Oggi le luci.

> Andamento termico globale perfettamente in linea con gli scenari degli ultimi rapporti IPCC (vedi qui)

> Sbilancio energetico planetario e accumulo di energia infrarossa in aumento, come da teoria (Murphy et al. 2009, Trenberth et al. 2009, von Schuckmann et al. 2009, Wild et al. 2007), con le misurazioni satellitari che mostrano una minor radiazione IR fuoriuscente nello spazio proprio nella lunghezza d'onda nella quale la CO2 assorbe energia, come da teoria (Griggs et al. 2004, Chen et al. 2007)

We examine the Earth's energy balance since 1950, identifying results that can be obtained without using global climate models. Important terms that can be constrained using only measurements and radiative transfer models are ocean heat content, radiative forcing by long-lived trace gases, and radiative forcing from volcanic eruptions. We explicitly consider the emission of energy by a warming Earth by using correlations between surface temperature and satellite radiant flux data and show that this term is already quite significant. About 20% of the integrated positive forcing by greenhouse gases and solar radiation since 1950 has been radiated to space. Only about 10% of the positive forcing (about 1/3 of the net forcing) has gone into heating the Earth, almost all into the oceans. About 20% of the positive forcing has been balanced by volcanic aerosols, and the remaining 50% is mainly attributable to tropospheric aerosols. After accounting for the measured terms, the residual forcing between 1970 and 2000 due to direct and indirect forcing by aerosols as well as semidirect forcing from greenhouse gases and any unknown mechanism can be estimated as −1.1 ± 0.4 W m−2 (1σ). This is consistent with the Intergovernmental Panel on Climate Change's best estimates but rules out very large negative forcings from aerosol indirect effects. Further, the data imply an increase from the 1950s to the 1980s followed by constant or slightly declining aerosol forcing into the 1990s, consistent with estimates of trends in global sulfate emissions. An apparent increase in residual forcing in the late 1990s is discussed.

Surface radiative forcing and temperature during the 1990s is not only determined by surface solar variations, but also strongly governed by the reduced thermal surface cooling with enhanced greenhouse capacity of the atmosphere, manifest in increased downward thermal radiation from the atmosphere to the surface. Evidence for increasing downward thermal radiation is obtained from the surface measurements of the BSRN [Ohmura et al., 1998], a project of the World Climate Research Program (WCRP) with its data centre at the authors’ institute, aimed at detecting important changes in the Earth’s radiation fields. Downward thermal radiation measured at 12 worldwide distributed sites from BSRN shows on average an increase of 0.26 Wm^-2 per year since the beginning of the measurements in 1992, in line with our expectations from greenhouse theory and models.
To estimate the integrated (overall) effect of variations in surface solar radiation over the past 40 years, we analysed the latest update of GEBA. In the majority of the surface solar radiation records from GEBA we find that, despite the widespread trend reversal from dimming to brightening, the amount of solar radiation at the surface has not reached the 1960 level. Despite the fact that surface insolation at the turn of the millennium is rather lower than in the 1960s, land surface temperatures have increased by 0.8C over this period (Figure 1). This suggests that the net
effect of surface solar forcing over the past decades cannot be the principal driver behind the overall temperature increase, since over the past 40 years, cooling from solar dimming still outweighs warming from solar brightening. Rather, the overall temperature increase since the 1960s can be attributed to greenhouse forcing as also evident in the BSRN data outlined above. Thus, speculations that solar brightening rather than the greenhouse effect could have been the main cause of the overall global warming over the past decades appear unfounded.

Previously published work using satellite observations of the clear sky infrared emitted radiation by the Earth in 1970, 1997 and in 2003 showed the appearance of changes in the outgoing spectrum, which agreed with those expected from known changes in the concentrations of well-mixed greenhouse gases over this period. Thus, the greenhouse forcing of the Earth has been observed to change in response to these concentration changes. In the present work, this analysis is being extended to 2006 using the TES instrument on the AURA spacecraft. Additionally, simulated spectra have been calculated using LBLRTM with inputs from the HadGEM1 coupled model and compared to the observed satellite spectra.

> Misurazioni superficiali denotano un aumento di radiazione IR dall'atmosfera verso la superficie terrestre (Philipona et al. 2004), in particolare nella banda di assorbimento della CO2, come da teoria (Evans 2006)

The earth's climate system is warmed by 35 C due to the emission of downward infrared radiation by greenhouse gases in the atmosphere (surface radiative forcing) or by the absorption of upward infrared radiation (radiative trapping). Increases in this emission/absorption are the driving force behind global warming. Climate models predict that the release of greenhouse gases into the atmosphere has altered the radiative energy balance at the earth's surface by several percent by increasing the greenhouse radiation from the atmosphere. With measurements at high spectral resolution, this increase can be quantitatively attributed to each of several anthropogenic gases. Radiance spectra of the greenhouse radiation from the atmosphere have been measured at ground level from several Canadian sites using FTIR spectroscopy at high resolution. The forcing radiative fluxes from CFC11, CFC12, CCl4, HNO3, O3, N2O, CH4, CO and CO2 have been quantitatively determined over a range of seasons. The contributions from stratospheric ozone and tropospheric ozone are separated by our measurement techniques. A comparison between our measurements of surface forcing emission and measurements of radiative trapping absorption from the IMG satellite instrument shows reasonable agreement. The experimental fluxes are simulated well by the FASCOD3 radiation code. This code has been used to calculate the model predicted increase in surface radiative forcing since 1850 to be 2.55 W/m2. In comparison, an ensemble summary of our measurements indicates that an energy flux imbalance of 3.5 W/m2 has been created by anthropogenic emissions of greenhouse gases since 1850. This experimental data should effectively end the argument by skeptics that no experimental evidence exists for the connection between greenhouse gas increases in the atmosphere and global warming.

> Permafrost artico degradante, come da ipotesi (Anisimov et al. 2006)

> Aumento del livello globale dei mari accelerante, come da ipotesi (Church et al. 2006)

> Perdita glaciale in Antartide accelerante, come da ipotesi (Velicogna et al. 2009), anche nella normalmente più stabile regione orientale (Chen et al. 2009)

> Perdita glaciale in Groenlandia accelerante, come da ipotesi (Velicogna et al. 2009)

We use monthly measurements of time-variable gravity from the GRACE (Gravity Recovery and Climate Experiment) satellite gravity mission to determine the ice mass-loss for the Greenland and Antarctic Ice Sheets during the period between April 2002 and February 2009. We find that during this time period the mass loss of the ice sheets is not a constant, but accelerating with time, i.e., that the GRACE observations are better represented by a quadratic trend than by a linear one, implying that the ice sheets contribution to sea level becomes larger with time. In Greenland, the mass loss increased from 137 Gt/yr in 2002–2003 to 286 Gt/yr in 2007–2009, i.e., an acceleration of −30 ± 11 Gt/yr2 in 2002–2009. In Antarctica the mass loss increased from 104 Gt/yr in 2002–2006 to 246 Gt/yr in 2006–2009, i.e., an acceleration of −26 ± 14 Gt/yr2 in 2002–2009. The observed acceleration in ice sheet mass loss helps reconcile GRACE ice mass estimates obtained for different time periods.

> Riduzione dei ghiacciai globali accelerante, come da ipotesi (WGMS 2008)

> Riduzione del pack artico accelerante, come da ipotesi, con il rateo di perdita che supera le proiezioni modellistiche di un fattore 3 (Stroeve et al. 2007)

> Quota della tropopausa in aumento, come da teoria (Santer 2003)

Observations indicate that the height of the tropopause—the boundary between the stratosphere and troposphere—has increased by several hundred meters since 1979. Comparable increases are evident in climate model experiments. The latter show that human-induced changes in ozone and well-mixed greenhouse gases account for 80% of the simulated rise in tropopause height over 1979–1999. Their primary contributions are through cooling of the stratosphere (caused by ozone) and warming of the troposphere (caused by well-mixed greenhouse gases).

> Raffreddamento e contrazione dell'alta atmosfera, consistentemente con gli effetti previsti (Lastovicka et al. 2008)

Abstract. In the upper atmosphere, greenhouse gases produce a cooling effect, instead of a warming effect. Increases in greenhouse gas concentrations are expected to induce substantial changes in the mesosphere, thermosphere, and ionosphere, including a thermal contraction of these layers. In this article we construct for the first time a pattern of the observed long-term global change in the upper atmosphere,
based on trend studies of various parameters. The picture we obtain is qualitative, and contains several gaps and a few discrepancies, but the overall pattern of observed long-term changes throughout the upper atmosphere is consistent with model predictions of the effect of greenhouse gas increases. Together with the large body of lower atmospheric trend research, our synthesis indicates that anthropogenic emissions of greenhouse gases are affecting the atmosphere at nearly all altitudes between ground and space.

> I jetstreams si stanno alzando di latitudine, mentre la fascia tropicale si sta espandendo, come da ipotesi (Archer et al. 2008, Seidel et al. 2007, Fu et al. 2006)

> Stiamo emettendo CO2 ad un ritmo tale che la sua concentrazione in atmosfera è ai livelli più alti almeno da 800'000 anni (Brook 2008) e molto probabilmente negli ultimi 15 milioni di anni (Tripati et al. 2009), con il più veloce rateo di crescita degli utlimi 22'000 anni (Joos et al. 2008).

[Climavariante]

Luci: evidenze dell'AGW.
Ombre: lacune e auspici nella modellizzazione futura del fenomeno.

Oggi le luci.

> Andamento termico globale perfettamente in linea con gli scenari degli ultimi rapporti IPCC (vedi qui)

> Sbilancio energetico planetario e accumulo di energia infrarossa in aumento, come da teoria (Murphy et al. 2009, Trenberth et al. 2009, von Schuckmann et al. 2009, Wild et al. 2007), con le misurazioni satellitari che mostrano una minor radiazione IR fuoriuscente nello spazio proprio nella lunghezza d'onda nella quale la CO2 assorbe energia, come da teoria (Griggs et al. 2004, Chen et al. 2007)







> Misurazioni superficiali denotano un aumento di radiazione IR dall'atmosfera verso la superficie terrestre (Philipona et al. 2004), in particolare nella banda di assorbimento della CO2, come da teoria (Evans 2006)



> Permafrost artico degradante, come da ipotesi (Anisimov et al. 2006)

> Aumento del livello globale dei mari accelerante, come da ipotesi (Church et al. 2006)

> Perdita glaciale in Antartide accelerante, come da ipotesi (Velicogna et al. 2009), anche nella normalmente più stabile regione orientale (Chen et al. 2009)

> Perdita glaciale in Groenlandia accelerante, come da ipotesi (Velicogna et al. 2009)




> Riduzione dei ghiacciai globali accelerante, come da ipotesi (WGMS 2008)

> Riduzione del pack artico accelerante, come da ipotesi, con il rateo di perdita che supera le proiezioni modellistiche di un fattore 3 (Stroeve et al. 2007)

> Quota della tropopausa in aumento, come da teoria (Santer 2003)



> Raffreddamento e contrazione dell'alta atmosfera, consistentemente con gli effetti previsti (Lastovicka et al. 2008)



> I jetstreams si stanno alzando di latitudine, mentre la fascia tropicale si sta espandendo, come da ipotesi (Archer et al. 2008, Seidel et al. 2007, Fu et al. 2006)

> Stiamo emettendo CO2 ad un ritmo tale che la sua concentrazione in atmosfera è ai livelli più alti almeno da 800'000 anni (Brook 2008) e molto probabilmente negli ultimi 15 milioni di anni (Tripati et al. 2009), con il più veloce rateo di crescita degli utlimi 22'000 anni (Joos et al. 2008).

Sbilancio energetico planetario e accumulo di energia infrarossa in aumento, come da teoria (Murphy et al. 2009, Trenberth et al. 2009, von Schuckmann et al. 2009, Wild et al. 2007), con le misurazioni satellitari che mostrano una minor radiazione IR fuoriuscente nello spazio proprio nella lunghezza d'onda nella quale la CO2 assorbe energia, come da teoria (Griggs et al. 2004, Chen et al. 2007)