<div dir="ltr"><div>One of the most common theories to question anthropogenic climate change is to reference the Medieval Warm Period and Little Ice Age during the past 1100 years,<br><a href="http://www.ncdc.noaa.gov/paleo/ctl/resource1000.html">http://www.ncdc.noaa.gov/paleo/ctl/resource1000.html</a><br>
as recent examples of natural climate variability, then to assert the warming of global average temperatures over the past 100 years is mostly a natural recovery from the LIA.  <br></div><div><br>Some climate scientists have questioned whether indeed there was a truly global climate shift that defined a MWP or LIA, pointing out these climate periods were more a regional phenomenon.<br>
</div><div><br></div>A just published online April 21, 2013 peer reviewed study in Nature Geoscience supports a more skeptical view of a truly global MWP or LIA, if I read the this paper correctly:<br><br><a href="http://www.nature.com/ngeo/journal/vaop/ncurrent/abs/ngeo1797.html">http://www.nature.com/ngeo/journal/vaop/ncurrent/abs/ngeo1797.html</a><br>
<div class="">
                                                                        <p class="">
                                                                        <span class="">Nature Geoscience</span><span class=""> |
                                        </span>Progress Article                           </p></div>

                        
                                                                                                                                                                                                                                                                                
                         
                         
                        
                                                
                                                                                                        
                                                        <h1 class="">Continental-scale temperature variability during the past two millennia</h1><dl class=""><dd class="">Nature Geoscience</dd><dd>(2013)</dd><dd class="">doi:10.1038/ngeo1797</dd></dl>

        <dl class=""><dt class="">Received</dt><dd>
                                                                                                                        09 December 2012
                                                                                                </dd><dt class="">Accepted</dt><dd>
                                                                                                                        11 March 2013
                                                                                                </dd><dt class="">Published online</dt><dd>
                                                                                                                                        
                                21 April 2013</dd></dl><h1 class="">Abstract</h1>
                                                
                                                                                                                                                <ul class=""><li class=""><span>Abstract</span><span class="">•</span></li><li><a href="http://www.nature.com/ngeo/journal/vaop/ncurrent/abs/ngeo1797.html#author-information">Author information</a><span class="">•</span></li>
<li class=""><a href="http://www.nature.com/ngeo/journal/vaop/ncurrent/abs/ngeo1797.html#supplementary-information">Supplementary information</a></li></ul>

                                
                                
                                                                                                
                                                                                                
                                                                        <p>Past global climate changes had strong regional expression. 
To elucidate their spatio-temporal pattern, we reconstructed past 
temperatures for seven continental-scale regions during the past one to 
two millennia. The most coherent feature in nearly all of the regional 
temperature reconstructions is a long-term cooling trend, which ended 
late in the nineteenth century. At multi-decadal to centennial scales, 
temperature variability shows distinctly different regional patterns, 
with more similarity within each hemisphere than between them. There 
were no globally synchronous multi-decadal warm or cold intervals that 
define a worldwide Medieval Warm Period or Little Ice Age, but all 
reconstructions show generally cold conditions between <span class="">ad</span>
 1580 and 1880, punctuated in some regions by warm decades during the 
eighteenth century. The transition to these colder conditions occurred 
earlier in the Arctic, Europe and Asia than in North America or the 
Southern Hemisphere regions. Recent warming reversed the long-term 
cooling; during the period <span class="">ad</span> 1971–2000, the area-weighted average reconstructed temperature was higher than any other time in nearly 1,400 years.</p><p>------------------------------------------</p>
<p>Vision2020 Post: Ted Moffett<br></p></div>