Browsing by Author "Ismail, Muhammad"
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Item Open Access Assessment of CMIP6 performance and projected temperature and precipitation changes over South America(Springer, 2021-06-17) Almazroui, Mansour; Ashfaq, Moetasim; Islam, M. Nazrul; Rashid, Irfan Ur; Kamil, Shahzad; Abid, Muhammad Adnan; O’Brien, Enda; Ismail, Muhammad; Reboita, Michelle Simões; Sörensson, Anna A.; Arias, Paola A.; Alves, Lincoln Muniz; Tippett, Michael K.; Saeed, Sajjad; Haarsma, Rein; Doblas‑Reyes, Francisco J.; Saeed, Fahad; Kucharski, Fred; Nadeem, Imran; Silva Vidal, Yamina; Rivera, Juan A.; Ehsan, Muhammad Azhar; Martínez-Castro, Daniel; Muñoz, Ángel G.; Ali, Md. Arfan; Coppola, Erika; Sylla, Mouhamadou BambaWe evaluate the performance of a large ensemble of Global Climate Models (GCMs) from the Coupled Model Intercomparison Project Phase 6 (CMIP6) over South America for a recent past reference period and examine their projections of twenty-first century precipitation and temperature changes. The future changes are computed for two time slices (2040–2059 and 2080–2099) relative to the reference period (1995–2014) under four Shared Socioeconomic Pathways (SSPs, SSP1–2.6, SSP2–4.5, SSP3–7.0 and SSP5–8.5). The CMIP6 GCMs successfully capture the main climate characteristics across South America. However, they exhibit varying skill in the spatiotemporal distribution of precipitation and temperature at the sub-regional scale, particularly over high latitudes and altitudes. Future precipitation exhibits a decrease over the east of the northern Andes in tropical South America and the southern Andes in Chile and Amazonia, and an increase over southeastern South America and the northern Andes—a result generally consistent with earlier CMIP (3 and 5) projections. However, most of these changes remain within the range of variability of the reference period. In contrast, temperature increases are robust in terms of magnitude even under the SSP1–2.6. Future changes mostly progress monotonically from the weakest to the strongest forcing scenario, and from the mid-century to late-century projection period. There is an increase in the seasonality of the intra-annual precipitation distribution, as the wetter part of the year contributes relatively more to the annual total. Furthermore, an increasingly heavy-tailed precipitation distribution and a rightward shifted temperature distribution provide strong indications of a more intense hydrological cycle as greenhouse gas emissions increase. The relative distance of an individual GCM from the ensemble mean does not substantially vary across different scenarios. We found no clear systematic linkage between model spread about the mean in the reference period and the magnitude of simulated sub-regional climate change in the future period. Overall, these results could be useful for regional climate change impact assessments across South America.Item Open Access Projected changes in temperature and precipitation over the United States, Central America, and the Caribbean in CMIP6 GCMs(Springer, 2021-01-29) Almazroui, Mansour; Islam, M. Nazrul; Saeed, Fahad; Saeed, Sajjad; Ismail, Muhammad; Ehsan, Muhammad Azhar; Diallo, Ismaila; O’Brien, Enda; Ashfaq, Moetasim; Martínez Castro, Daniel; Cavazos, Tereza; Cerezo‑Mota, Ruth; Tippett, Michael K.; Gutowski Jr., William J.; Alfaro, Eric J.; Hidalgo, Hugo G.; Vichot‑Llano, Alejandro; Campbell, Jayaka D.; Kamil, Shahzad; Rashid, Irfan Ur; Sylla, Mouhamadou Bamba; Stephenson, Tannecia; Taylor, Michael; Barlow, MathewThe Coupled Model Intercomparison Project Phase 6 (CMIP6) dataset is used to examine projected changes in temperature and precipitation over the United States (U.S.), Central America and the Caribbean. The changes are computed using an ensemble of 31 models for three future time slices (2021–2040, 2041–2060, and 2080–2099) relative to the reference period (1995–2014) under three Shared Socioeconomic Pathways (SSPs; SSP1-2.6, SSP2-4.5, and SSP5-8.5). The CMIP6 ensemble reproduces the observed annual cycle and distribution of mean annual temperature and precipitation with biases between − 0.93 and 1.27 °C and − 37.90 to 58.45%, respectively, for most of the region. However, modeled precipitation is too large over the western and Midwestern U.S. during winter and spring and over the North American monsoon region in summer, while too small over southern Central America. Temperature is projected to increase over the entire domain under all three SSPs, by as much as 6 °C under SSP5-8.5, and with more pronounced increases in the northern latitudes over the regions that receive snow in the present climate. Annual precipitation projections for the end of the twenty-first century have more uncertainty, as expected, and exhibit a meridional dipole-like pattern, with precipitation increasing by 10–30% over much of the U.S. and decreasing by 10–40% over Central America and the Caribbean, especially over the monsoon region. Seasonally, precipitation over the eastern and central subregions is projected to increase during winter and spring and decrease during summer and autumn. Over the monsoon region and Central America, precipitation is projected to decrease in all seasons except autumn. The analysis was repeated on a subset of 9 models with the best performance in the reference period; however, no significant difference was found, suggesting that model bias is not strongly influencing the projections.