Index: trunk/resources/data/validator/numeric.mapcss
===================================================================
--- trunk/resources/data/validator/numeric.mapcss	(revision 18757)
+++ trunk/resources/data/validator/numeric.mapcss	(revision 19129)
@@ -663,2 +663,12 @@
   assertNoMatch: "node name=\"1. Chemnitzer Billardclub 1952 e.V.\"";
 }
+
+/* #23621 */
+node[natural=tree][circumference][siunit_length(tag(circumference)) > 45] {
+  throwWarning: tr("Unusually large value of {0} in meters, possibly centimeter units are meant?", "{0.key}");
+  assertMatch: "node natural=tree circumference=200";
+  assertMatch: "node natural=tree circumference=82.4";
+  assertNoMatch: "node natural=tree circumference=18.4";
+  assertNoMatch: "node natural=tree circumference=\"100 cm\"";
+  assertNoMatch: "node natural=tree circumference=43"; /* Current world record */
+}