Characterizing and attributing the warming trend in sea and land surface temperatures

Abstract

RESUMENDebido a la variabilidad interna de baja frecuencia, las tendencias del calentamiento observadas y subyacentes en series de temperatura pueden ser marcadamente diferentes. Las temperaturas hemisféricas están caracterizadas por importantes discrepancias en las tendencias no lineales observadas, sugiriendo que los hemisferios norte y sur han respondido de manera diferente a los cambios en el forzamiento radiativo. Mediante la utilización de técnicas econométricas recientes es posible reconciliar estas diferencias y mostrar que todas las temperaturas terrestres y oceánicas comparten propiedades de series de tiempo similares, así como una tendencia subyacente común de origen antrópico. También se investiga la asimetría inter-hemisférica de temperatura (ITA, por sus siglas en inglés) y se muestra que la diferencia en el calentamiento entre hemisferios se debe en parte al forzamiento antrópico, pero que la mayoría de los cambios rápidos observados son probablemente producto de la variabilidad natural. La atribución de cambios en la ITA es importante porque los aumentos en el contraste de temperaturas entre hemisferios podrían ocasionar un desplazamiento de la zona intertropical de convergencia y alterar los patrones de precipitación. También se investigan la existencia y causas de una reciente ralentización en el calentamiento. Los resultados sugieren que dicha lentificación es una característica común de las temperaturas hemisféricas globales tanto en tierra como en el océano, y que puede atribuirse al menos parcialmente a cambios en el forzamiento antrópico. ABSTRACTBecause of low-frequency internal variability, the observed and underlying warming trends in temperature series can be markedly different. Important differences in the observed nonlinear trends in hemispheric temperature series suggest that the northern and southern hemispheres have responded differently to the changes in the radiative forcing. Using recent econometric techniques, we can reconcile such differences and show that all sea and land temperatures share similar time series properties and a common underlying warming trend having a dominant anthropogenic origin. We also investigate the interhemispheric temperature asymmetry (ITA) and show that the differences in warming between hemispheres are in part driven by anthropogenic forcing but that most of the observed rapid changes is likely due to natural variability. The attribution of changes in ITA is relevant since increases in the temperature contrast between hemispheres could potentially produce a shift in the Intertropical Convergence Zone and alter rainfall patterns. The existence of a current slowdown in the warming and its causes are also investigated. The results suggest that the slowdown is a common feature in global and hemispheric sea and land temperatures that can, at least partly, be attributed to changes in anthropogenic forcing.

Modes of climate variability and their relationships with interhemispheric temperature asymmetry: a Granger causality analysis

“…For the interhemispheric temperature asymmetry, natural variability partially masks the underlying anthropogenic global warming signal. This conclusion seems to be consistent with the evidence that Estrada et al (2017) have recently provided using a different statistical methodology. However, since AMO should be primarily controlled by external forcing, we want to study the relationship between AMO and ITA removing the forced signal in future research.…”

“…It is important to note that the analysis of the ITA time plot may suggest the existence of a structural break in the late 1960s. Estrada et al (2017), by applying the Perron-Yabu (PY) test to ITA, formally document the existence of a break in both the level and the slope of the trend -1967:12 and 1968:01-2016:12. The HQ criterion has selected p = 2 also in these sample periods.…”

Spatial variations in the warming trend and the transition to more severe weather in midlatitudes

“…Although in some cases efforts are done to reduce the influence of external forcings (i.e., AMO is usually linearly detrended), part of this influence remains 35 . While separation of external forcing and natural variability in these indices is imperfect, it has been shown that they are useful in purging out low-frequency oscillations while retaining the trend produced by the response to changes in external forcing 3 , 27 , 28 , 37 , 39 . What is important is to get rid of the most of the low frequency movements associated with natural variability in order to get a more precise estimate of the break date.…”

“…Whether anthropogenic influences are factors driving climate/weather patterns in midlatitudes can be investigated by analyzing the spatial–temporal patterns of the response to increases in external forcings, the main common features of the regional temperature trends. Recent attribution studies showed that total and anthropogenic forcings are characterized by two marked changes in trend slope 3 , 4 , 27 , 28 , which are imparted to global and hemispheric temperatures, producing a temporal co-breaking pattern interpreted as a strong causality effect from anthropogenic forcing to temperatures 5 . The first is a marked increase in the rate of both forcings and warming near 1960, inducing the onset of the sustained global warming.…”

Global Land Surface Temperature Influenced by Vegetation Cover and PM2.5 from 2001 to 2016

“…Climate change has widely impacted human society and the natural environment, and an increasing number of studies have researched global warming [1]. According to the Intergovernmental Panel on Climate Change (IPCC) Fifth Assessment Report (AR5), the average global surface temperature increased by approximately 0.85 • C from 1880 to 2010 [2].…”