2. Agotamiento de modelo y crisis de poder
4.2 El interés nacional como premisa de la política exterior
3212 3213 3214
Just as the detection of terrestrial responses to solar activity initially signified the relevance of
3215
solar radiative forcing for understanding climate change, in lieu of direct observations of the
3216
forcing itself, so too does ongoing analyses of ever-lengthening terrestrial observations and
3217
newly extracted, high fidelity paleoclimate records continue to strengthen and expand the
3218
evidence. Using indicators such as sunspots and cosmogenic isotopes to identify times of high
3219
and low solar activity during the 11-, 80- and 210-year cycles, solar-related changes are
3220
identified in diverse climate parameters that range from low latitude drought and rainfall (e.g.,
3221
Verschuren et al., 2000; Neff et al., 2001; Haug et al., 2003; Antico & Torres, 2015), associated
3222
with Intertropical Convergence Zone displacement (Novello et al., 2016) and a La-Nina type
3223
response in the tropical Pacific (Mann et al., 2005), to mid-and high latitude ‘centers of action’
3224
(Christoforou & Hameed, 1997), storm tracks and winter intensity (e.g., Barriopedro et a., 2008;
3225
Mann et al., 2009; Lockwood et al., 2010), associated with the North Atlantic Oscillation and
3226
the circumpolar vortex.
3227 3228
On global scales, climate signals related to the 11-year solar cycle were detected first in basin‐
3229
wide ocean temperatures (White et al., 1997) then in global lower tropospheric temperature
3230
(Michaels & Knappenberger, 2000). Observational temperature and ozone databases are now
3231
sufficiently long that statistical analyses readily isolate in them solar responses, both globally
3232
and regionally, from other concurrent influences (Douglass & Clader, 2002; Lean and Rind,
3233
2008; Foster & Rahmstorf, 2011). Figure 8.3 shows the solar cycle component, thus extracted,
3234
of <0.1oC in global surface temperature and <3 DU (1%) in total ozone compared with natural
3235 3236
(volcanic, ENSO, QBO) and anthropogenic (greenhouse gases and ozone depleting substances)
3237
components and Figure 8.4 shows the corresponding geographical response patterns. These
3238
estimates of climate’s response to solar forcing are attained by linearly regressing indices of the
3239
simultaneous natural and anthropogenic influences against (de-seasonalized) monthly mean surface
3240
temperature (Figure 8.3a) and total ozone (Figure 8.3b) observations from 1979 to 2017 (Lean,
3241
2017, 2018b). 3242
3243
Time dependent simulations of climate’s response to solar radiative forcing on climatological
3244
time scales became possible with the reconstruction of historical solar irradiance. Simulations
3245
using energy balance models initially suggested that the global surface temperature response to
3246
reconstructed solar irradiance cycles since 1874 (Foukal & Lean, 1990) was likely undetectable,
3247
the transient response of 0.03°C being notably smaller than the equilibrium response because of
3248
attenuation (~80%) by the thermal inertia of the ocean (Wigley & Raper, 1990). But subsequent
3249
analysis of historical surface temperature observations did detect a solar cycle response of
3250
0.06°C by statistically extracting the modelled spatial pattern of the response to the forcing
3251
(Stevens & North, 1996).
3252 3253
The first general circulation model simulations of climate’s response to time-dependent solar
3254
radiative forcing found a global surface temperature increase of ~0.5°C since the Maunder
3255
Minimum (Cubacsh et al., 1997; Rind et al., 1999). Decreased solar irradiance during the
3256
Spörer, Maunder and Dalton solar activity minima (Eddy, 1976) and enhanced volcanic activity
3257
are posited causes of anomalously cold surface temperatures from ~1300 to 1850, during the
3258
Little Ice Age (e.g., Mann et al., 2005, 2009). Even though the simulations input a factor of five
(Wang et al., 2005), they nevertheless identified that water vapor feedbacks, cloud cover
3261
changes and land-sea contrasts contribute to the surface response to solar radiative forcing, with
3262
enhanced warming in sub-tropical regions similar to that forced by increasing greenhouse gas
3263
concentrations. The simulations further established that variations in solar irradiance were
3264
unlikely to be the primary cause of global warming in the postindustrial period, as some
3265
statistical correlations between solar cycle length and northern hemisphere temperature had
3266
suggested (Friis-Christensen & Lassen, 1991).
3267 3268
State-of-the-art general circulation models now include couplings between the land, ocean and
3269
atmosphere, functional middle atmospheres with ozone chemistry, and the ability to input
3270
realistic solar spectral irradiance changes. Analyses of ensembles of simulations made with
3271
various such models, designed to isolate responses of different terrestrial regimes to solar
3272
radiative forcing, demonstrate both a direct response of the land and ocean, dependent in part on
3273
the regional distribution of clouds, and an indirect response facilitated by stratospheric ozone
3274
and temperature changes (Rind et al., 2008; Meehl et al., 2009). Convective and dynamical
3275
processes disperse the forcing geographically and altitudinally, altering extant dynamical
3276
patterns such as the Hadley and Walker circulations and impacting, in particular, the
3277
hydrological cycle. IPCC’s AR5 climate assessment included simulations made with 13 models
3278
that resolve the stratosphere (Mitchell et al., 2015), 6 of which include interactive ozone
3279
chemistry (Hood et al., 2015). Modeled responses to solar cycle irradiance changes are evident
3280
at the surface, in the ocean (Misios et al., 2015) and in the troposphere, stratosphere and ozone
3281
layer (Hood et al., 2015). While the simulated responses are generally of smaller magnitude
3282
than in observations (e.g., global mean surface warming of 0.07oC), the processes and patterns
are qualitatively similar, including changes in precipitation and water vapor leading to weaker
3284
Walker circulation (Misios et al., 2015) and a stratosphere-related North Atlantic surface
3285
response (Mitchell et al., 2015).
3286 3287
Figure 8.4 compares statistically-extracted geographical patterns of the terrestrial response to
3288
solar radiative forcing with estimates made by a physical climate model (Rind et al., 2008).
3289
Differences between the physical and statistical model patterns suggest that deficiencies remain
3290
in one or both. Uncertainties in the hundreds of parameterizations that seek to account for the
3291
multiple integrated processes that heat the land and ocean, and redistribute this heat regionally
3292
and vertically, compromise physical model simulations. Statistical models suffer from
3293
uncertainties in the predictors and covariance among them (such as between solar and
3294
anthropogenic indices), including distinguishing whether covariance is physically based or
3295
random. The limited duration of the most reliable observations and indices exacerbate such
3296
uncertainties. Articulating and reconciling differences between the statistical and physical
3297
models is expected to improve understanding of process that facilitate terrestrial responses to
3298
solar radiative forcing, and may help improve physical model parameterizations of these
3299
processes. It is increasingly apparent that solar radiative forcing initiates a continuous spectrum
3300
of coupled interactions throughout Earth’s land, ocean and atmosphere on multiple time scales
3301
with different and interrelated regional dependencies. Differential heating of the land and
3302
oceans, equator and poles, and surface and atmosphere drive these responses; the processes
3303
involved are those by which climate responds to other radiative forcings, including by
3304
increasing greenhouse gas concentrations, albeit with different, magnitude, timing and regional
3305
detail.
3307